Physics 2020 Midterm

A charge Q accumulates on the hollow metallic dome, of radius R, of a Van de Graaff generator. A probe measures the electric field strength at various points outside the sphere surface. If the probe is initially at a distance 3R from the sphere's center and then is moved to 4R, by what factor will the electric field reading change?

(3/4)^2

A charge Q accumulates on the hollow metallic dome, of radius R, of a Van de Graaff generator. A probe measures the electric field strength at various points outside the sphere surface. By what factor will the electric field value at the 2R distance be changed if the charge value were increased to (4/3)Q?

(4/3)^2 ?

An initially uncharged hollow metallic sphere with radius of 5 cm has a small object with a charge of +10 µC carefully placed at the center of the sphere through a hole in the latter's surface. With the charge in place, what charge is now present on the outside surface of the sphere?

+10 µC

We have a hollow metallic sphere with charge -5.0 µC and radius 5.0 cm. We insert a +10-µC charge at the center of the sphere through a hole in the surface. What charge now rests on the outer surface of the sphere?

+5 µC

Four charges are at the corners of a square, with B and C on oppositecorners. Charges A and D, on the other two corners, have equal charge, while both B and C have a charge of +1.0 C. What is the charge on A so that the force on B is zero?

-0.35 C

Q1 has 50 electric field lines radiating outward and Q2 has 100 field lines converging inward. What is the ratio Q1/Q2?

-1/2

An initially uncharged hollow metallic sphere with radius of 5 cm has a small object with a charge of +10 µC carefully placed at the center of the sphere through a hole in the latter's surface. What charge resides inner surface of the sphere?

-10 µC

In the circuit segment shown if I = 7 mA and Q = 50 µC, what is the potential difference, VA - VB?

-20 V

Two point charges are placed along a horizontal axis with the following values and positions: +3.0 µC at x = 0 cm and -7.0 µC at x = 20 cm. At what point along the x axis is the electric field zero?

-38 cm

A charge of +2 C is at the origin. When charge Q is placed at 2 m along the positive x axis, the electric field at 2 m along the negative x axis becomes zero. What is the value of Q?

-8 C

Two equal charges, each Q, are separated by some distance. What third charge would need to be placed half way between the two charges so that the net force on each charge would be zero?

-Q/4

A thin uncharged conducting spherical shell has a charge q carefully placed at its center through a small hole in the shell. The charge q does not touch the shell. What is the charge on the shell?

0

Two identical iron spheres have equal positive charges and the force between them when they are 1 m apart is 1 N. What percentage of the electrons has been removed from each sphere if each sphere has 1 mole (6 ´ 1023) of iron atoms? (ke = 8.99 ´ 109 N×m2/C2, the atomic number of iron is 26, and the electron charge is -1.6 ´ 10-19 C)

0.001% ?

A certain material is in a room at 27°C. If the absolute temperature (K) of the material is tripled, its resistance doubles. (Water freezes at 273 K.) What is the value for a, the temperature coefficient of resistivity?

0.0017 (°C)-1

A 10-turn square coil of area 0.036 m2 and a 20-turn circular coil are both placed perpendicular to the same changing magnetic field. The voltage induced in each of the coils is the same. What is the area of the circular coil?

0.018 m^2

A coil with a self-inductance of 0.75 mH experiences a constant current buildup from zero to 10 A in 0.25 s. What is the induced emf during this interval?

0.030 V

A circular loop carrying a current of 1.0 A is oriented in a magnetic field of 0.35 T. The loop has an area of 0.24 m2 and is mounted on an axis, perpendicular to the magnetic field, which allows the loop to rotate. What is the torque on the loop when its plane is oriented at a 25° angle to the field?

0.076 N×m

A circular loop carrying a current of 1.0 A is oriented in a magnetic field of 0.35 T. The loop has an area of 0.24 m2 and is mounted on an axis, perpendicular to the magnetic field, which allows the loop to rotate. If the plane of the loop is oriented parallel to the field, what torque is created by the interaction of the loop current and the field?

0.084 N×m

A proton initially moves left to right long the x axis at a speed of 2.00 ´ 103 m/s. It moves into an electric field, which points in the negative x direction, and travels a distance of 0.200 m before coming to rest. If the proton's mass and charge are 1.67 ´ 10-27 kg and 1.60 ´ 10-19 C respectively, what is the magnitude of the electric field?

0.104 N/C

A 1 000-V battery, a 3 000-W resistor and a 0.50-mF capacitor are connected in series with a switch. The time constant for such a circuit, designated by the Greek letter, , is defined as the time that the capacitor takes to charge to 63% of its capacity after the switch is closed. What is the current in the circuit at a time interval of seconds after the switch has been closed?

0.12 A

The resistance of a platinum wire is to be calibrated for low-temperature work. A platinum wire with resistance 1.000 W at 20°C is immersed in liquid nitrogen at 77 K (-196°C). If the temperature response of the platinum wire is linear, what is the expected resistance of the platinum wire at -196°C? aplatinum = 3.92 ´ 10-3 (°C)-1

0.153 W

If e = 9.0 V, what is the current in the 15-W resistor?

0.20 A

A square coil, enclosing an area with sides 2.0 cm long, is wrapped with 2 500 turns of wire. A uniform magnetic field perpendicular to its plane is turned on and increases to 0.25 T during an interval of 1.0 s. What average voltage is induced in the coil?

0.25 V

A uniform 4.5-T magnetic field passes through the plane of a wire loop 0.10 m2 in area. What flux passes through the loop when the direction of the 4.5-T field is at a 30° angle to the normal of the loop plane?

0.39 T×m^2

A series RC circuit has a time constant of 1.0 s. The battery has a voltage of 50 V and the maximum current just after closing the switch is 500 mA. The capacitor is initially uncharged. What is the charge on the capacitor 2.0 s after the switch is closed?

0.43 C

A uniform 4.5-T magnetic field passes perpendicularly through the plane of a wire loop 0.10 m2 in area. What flux passes through the loop?

0.45 T×m^2

A resistor is connected to a battery with negligible internal resistance. If you replace the resistor with one that has twice the resistance, by what factor does the power dissipated in the circuit change?

0.50

A 60-W light bulb is in a socket supplied with 120 V. What is the current in the bulb?

0.50 A

A light bulb has resistance of 240 W when operating at 120 V. Find the current in the light bulb

0.50 A

What is the current through the 8-W resistor?

0.50 A ? maybe 1.5 A

A circular coil (radius = 0.40 m) has 160 turns and is in a uniform magnetic field. If the orientation of the coil is varied through all possible positions, the maximum torque on the coil by magnetic forces is 0.16 N×m when the current in the coil is 4.0 mA. What is the magnitude of the magnetic field?

0.50 T

A coil in a magnetic field encloses a flux of 0.256 T·m2 when the angle between the normal to the coil and the direction of the magnetic field is 70.0°. What flux would go through the coil if the angle were changed to 40.0°?

0.573 T·m^2

Three resistors connected in parallel have individual values of 4.0, 6.0 and 10.0 W, respectively. If this combination is connected in series with a 12-V battery and a 2.0-W resistor, what is the current in the 10-W resistor?

0.59 A

A current-carrying wire of length 50 cm is positioned perpendicular to a uniform magnetic field. If the current is 10.0 A and it is determined that there is a resultant force of 3.0 N on the wire due to the interaction of the current and field, what is the magnetic field strength?

0.60 T

How much current is flowing in one of the 10-W resistors

0.8 A

An emf of 0.32 V is induced in a 0.40-H inductor. What is the rate of change of current through the inductor?

0.80 A/s

A copper cable needs to carry a current of 200 A with a power loss of only 3.0 W/m. What is the required radius of the copper cable? (The resistivity of copper is 1.7 ´ 10-8 W×m.)

0.85 cm

When a 24.0-W resistor is connected across a 12.0-V battery, a current of 482 mA flows. What is the internal resistance of the battery?

0.9 W

If a lamp has a resistance of 120 W when it operates at 100 W, what current does it carry?

0.91 A

A nichrome wire has a radius of 0.50 mm and a resistivity of 1.5 ´ 10-6 W×m. If the wire carries a current of 0.50 A, what is the potential difference per unit length along this wire?

0.95 V/m

Two singly ionized isotopes, X and Y, of the same element move with the same speed perpendicular to a uniform magnetic field. Isotope X follows a path of radius 3.35 cm while isotope Y moves along a path 3.43 cm in radius. What is the ratio of the two isotope masses, mX/mY

0.977

A proton and a deuteron are moving with equal velocities perpendicular to a uniform magnetic field. A deuteron has the same charge as the proton but has twice its mass. The ratio of the magnetic force on the proton to that on the deuteron is:

1

A 1 000-V battery, a 3 000-W resistor and a 0.50-µF capacitor are connected in series with a switch. The capacitor is initially uncharged. What is the value of the current the moment after the switch is closed?

1.0 A ? maybe 0.33 A

Two long parallel wires 40 cm apart are carrying currents of 10 A and 20 A in the same direction. What is the magnitude of the magnetic field halfway between the wires?

1.0 x 10^-5 T

Two long parallel wires 40 cm apart are carrying currents of 10 A and 20 A in the opposite direction. What is the magnitude of the magnetic field halfway between the wires?

1.0 x 10^-5 T ? maybe 3 x 10^-5 T

A proton initially moves left to right long the x axis at a speed of 2.00 ´ 103 m/s. It moves into an electric field, which points in the negative x direction, and travels a distance of 0.200 m before coming to rest. What acceleration magnitude does the proton experience?

1.00 x 10^7 m/s^2

Three resistors, with values of 2.0, 4.0 and 8.0 W, respectively, are connected in parallel. What is the overall resistance of this combination?

1.1 W

In x-ray machines, electrons are subjected to electric fields as great as 6.0 ´ 105 N/C. Find an electron's acceleration in this field. (me = 9.11 ´ 10-31 kg, e = 1.6 ´ 10-19 C)

1.1 x 10^17 m/s^2

A 12-V battery is connected in series with a switch, resistor and coil. If the circuit's time constant is 2.0 ´ 10-4 s and the final steady current after the switch is closed becomes 1.0 A, what is the value of the inductance?

1.2 mH

A steam turbine at an electric power plant delivers 4 500 kW of power to an electrical generator which converts 95% of this mechanical energy into electrical energy. What is the current delivered by the generator if it delivers at 3 600 V?

1.2 x 10^3 A

A ping-pong ball covered with a conducting graphite coating has a mass of 5.0 ´ 10-3 kg and a charge of 4.0 µC. What electric field directed upward will exactly balance the weight of the ball? (g = 9.8 m/s2)

1.2 x 10^4 N/C

Number 10 copper wire (radius = 1.3 mm) is commonly used for electrical installations in homes. What is the voltage drop in 40 m of #10 copper wire if it carries a current of 10 A? (The resistivity of copper is 1.7 ´ 10-8 W×m.)

1.3 V

A Van de Graaff generator has a spherical dome of radius 20 cm. Operating in dry air, where "atmospheric breakdown" is at Emax = 3.0 ´ 106 N/C, what is the maximum charge that can be held on the dome? (ke = 8.99 ´ 109 N×m2/C2)

1.3 x 10^-5 C

Charge A and charge B are 3.00 m apart, and charge A is +2.00 C and charge B is +3.00 C. Charge C is located between them at a certain point and the force on charge C is zero. How far from charge A is charge C?

1.35 m

By what factor is the resistance of a copper wire changed when its temperature is increased from 20°C to 120°C? The temperature coefficient of resistivity for copper = 3.9 ´ 10-3 (°C)-1.

1.39

A proton moving at a speed of 3.8 ´ 106 m/s cuts across the lines of a magnetic field at an angle of 70°. The strength of the field is 0.25 ´ 10-4 T. What is the magnitude of the force acting on the proton? (qp = 1.6 ´ 10-19 C)

1.4 x 10^-17 N

A circuit contains a 6.0-V battery, a 4.0-W resistor, a 0.60-µF capacitor, an ammeter, and a switch all in series. What will be the current reading immediately after the switch is closed?

1.5 A

What is the current through the 2-W resistor?

1.5 A ? maybe 1.0 A

Two loops of wire are arranged so that a changing current in one, the primary, will induce a current in the other, the secondary. The secondary loop has twice as many turns as the primary loop. As long as the current in the primary is steady at 3 A, the current in the secondary will be:

1.5 A? maybe zero

A 500-W heater carries a current of 4.0 A. How much does it cost to operate the heater for 30 min if electrical energy costs 6.0 cents per kWh?

1.5 cents

If I = 2.0 mA and the potential difference, VA - VB = +30 V in the circuit segment shown, determine the charge and polarity of the capacitor.

1.5 mC, left plate is positive

A series circuit contains a 12-V battery, a 2.0-W resistor, and a 3.0-mH inductor. If the switch to the battery is closed at t = 0, find the time required for the current in the circuit to reach 63% of its final value.

1.5 ms

A 1 000-V battery, a 3 000-W resistor and a 0.50-µF capacitor are connected in series with a switch. The time constant for such a circuit, designated by the Greek letter, , is defined as the time required to charge the capacitor to 63% of its capacity after the switch is closed. What is the value of for this circuit?

1.5 x 10^-3 s

If e = 20 V, at what rate is thermal energy being generated in the 20-W resistor?

1.6 W

A superconducting wire carries a current of 104 A. Find the magnetic field at a distance of 1.0 m from the wire. (µ0 = 4p ´ 10-7 T×m/A)

1.6 x 10^-2 T ? maybe 2*10^-3 T

A horizontal wire of length 3.0 m carries a current of 6.0 A and is oriented so that the current direction is 50° S of W. The Earth's magnetic field is due north at this point and has a strength of 0.14 ´ 10-4 T. What is the size of the force on the wire?

1.6 x 10^-4 N

A 100-m-long wire carrying a current of 4.0 A will be accompanied by a magnetic field of what strength at a distance of 0.050 m from the wire? (magnetic permeability in empty space µ0 = 4p ´ 10-7 T×m/A)

1.6 x 10^-5 T

A nichrome wire has a radius of 0.50 mm and a resistivity of 1.5 ´ 10-6 W×m. What is the resistance per unit length of this wire?`

1.9 W/M

**If the distance between two point charges is tripled, the mutual force between them will be changed by what factor?

1/9

Replacing a wire resistor with another of the same material and length but with three times the diameter will have the effect of changing the resistance by what factor?

1/9

If the size of the charge value is tripled for both of two point charges maintained at a constant separation, the mutual force between them will be changed by what factor?

1/9 ?

Resistors of values 6.0W, 4.0W, 10.0W and 7.0W are combined as shown. What is the equivalent resistance for this combination?

10.7 W

A high-voltage transmission line carries 1 000 A at 700 kV for a distance of 100 miles. If the resistance in the wire is 1 W/mile, what is the power loss due to resistive losses?

100 MW

Niobium metal becomes a superconductor (with electrical resistance equal to zero) when cooled below 9 K. If superconductivity is destroyed when the surface magnetic field exceeds 0.100 T, determine the maximum current a 4.00-mm-diameter niobium wire can carry and remain superconducting. (µ0 = 4p ´ 10-7 T×m/A)

1000 A

Different units can be used to measure the same physical quantity, differing only by some multiplicative factor. The cgs unit for magnetic field, the gauss, is equal to ____ tesla.

10^-4

About how many electrons are in 30 grams of water (H2O)?

10^25

An electric toaster requires 1 100 W at 110 V. What is the resistance of the heating coil?

11.0 W

An electric motor draws a current of 2.50 A from a 15.0-V battery when it runs at normal speed. If the motor's armature is "jammed" so that it cannot rotate, the current suddenly rises to 10.0 A. What is the back emf of the motor when running at normal speed?

11.3 V

When a 24.0-W resistor is connected across a 12.0-V battery, a current of 482 mA flows. What is the resulting terminal voltage of the battery?

11.6 V

If a lamp has resistance of 120 W when it operates at 100 W, what is the applied voltage?

110 V

A solar panel measures 80 cm ´ 50 cm. In direct sunlight, the panel delivers 3.2 A at 15 V. If the intensity of sunlight is 1 000 W/m2, what is the efficiency of the solar panel in converting solar energy into electrical energy?

12%

An RL series circuit has: 5.0-mH coil, 1.0-W resistor, 12-V battery, ammeter and switch. After the switch is closed for a long time, find the final value of the current

12.0 A

A 500-turn circular coil with an area of 0.050 0 m2 is mounted on a rotating frame that turns at a rate of 20.0 rad/s in the presence of a 0.050 0-T uniform magnetic field that is perpendicular to the axis of rotation. What is the instantaneous emf in the coil at the moment that the normal to its plane is at a 30.0° angle to the field?

12.5 V

A 500-turn circular coil with an area of 0.050 0 m2 is mounted on a rotating frame, which turns at a rate of 20.0 rad/s in the presence of a 0.050 0-T uniform magnetic field that is perpendicular to the axis of rotation. What is the instantaneous emf in the coil at the moment that the normal to its plane is at a 90.0° angle to the field?

12.5 V ?

Superconductors can carry very large currents with no resistance. If a superconducting wire is formed into a solenoid of length 50.0 cm with 500 turns, what is the magnetic field inside the solenoid when the current is 104 A? (µ0 = 4p ´ 10-7 T×m/A)

12.6 T

If a 500-W heater carries a current of 4.00 A, what is the voltage across the ends of the heating element?

125 V

If e = 24 V, at what rate is thermal energy generated in the 20-W resistor?

13 W

Suppose that a voltage surge produces 140 V for a moment in a 120-V line. What will temporarily be the output of a 100-W light bulb assuming its resistance does not change?

136 w

Three resistors, with values of 2.0, 4.0 and 8.0 W, respectively, are connected in series. What is the overall resistance of this combination?

14.0 W

Two identical spheres each carry a charge of -40.0 µC. The spheres are separated by a distance of 1.00 m. What is the electric force between the spheres? (ke = 8.99 ´ 109 N·m2/C2)

14.4 N (repulsive)

Two point charges are separated by 10.0 cm and have charges of +2.00 µC and -2.00 µC, respectively. What is the electric field at a point midway between the two charges? (ke = 8.99 ´ 109 N·m2/C2)

14.4 x 10^6 N/C

The electric field in a cathode ray tube is supposed to accelerate electrons from 0 to 1.60 ´ 107 m/s in a distance of 2.00 cm. What electric field is required? (me = 9.11 ´ 10-31 kg and e = 1.60 ´ 10-19 C)

146 000 N/C ?

The current in a coil with a self-inductance of 1.5 mH increases from 0 to 1.0 A in a tenth of a second. What is the induced emf in the coil?

15 mV

A tungsten wire is used to determine the melting point of indium. The resistance of the tungsten wire is 3.000 W at 20°C and increases to 4.850 W as the indium starts to melt. atungsten = 4.50 ´ 10-3 (°C)-1. What is the melting temperature of indium?

157 degrees C

In a circuit, a current of 2.0 A is drawn from a battery. The current then divides and passes through two resistors in parallel. One of the resistors has a value of 64 W and the current through it is 0.40 A. What is the value of the other resistor?

16 W

A rectangular loop (area = 0.15 m2) turns in a uniform magnetic field with B = 0.20 T. At an instant when the angle between the magnetic field and the normal to the plane of the loop is p/2 rads and increasing at the rate of 0.60 rad/s, what is the magnitude of the emf induced in the loop?

18 mV

A voltage source of 10 V is connected to a series RC circuit where R = 2.0 ´ 106 W, and C = 3.0 µF. Find the amount of time required for the current in the circuit to decay to 5% of its original value. Hint: This is the same amount of time for the capacitor to reach 95% of its maximum charge.

18 s

A metallic conductor has a resistivity of 18 ´ 10-6 W×m. What is the resistance of a piece that is 30 m long and has a uniform cross sectional area of 3.0 ´ 10-6 m2?

180 W

A proton and a deuteron are moving with equal velocities perpendicular to a uniform magnetic field. A deuteron has the same charge as the proton but has twice its mass. The ratio of the acceleration of the proton to that of the deuteron is:

2

Electrons in a particle beam each have a kinetic energy of 3.2 ´ 10-17 J. What is the magnitude of the electric field that will stop these electrons in a distance of 0.1 m? (e = 1.6 ´ 10-19 C)

2 000 N/C

An electron moves through a region of crossed electric and magnetic fields. The electric field E = 2 000 V/m and is directed straight down. The magnetic field B = 0.80 T and is directed to the left. For what velocity v of the electron into the paper will the electric force exactly cancel the magnetic force?

2 500 m/s

A wire carries a steady current of 0.1 A over a period of 20 s. What total charge passes through the wire in this time interval?

2 C

A copper wire of length 25 cm is in a magnetic field of 0.20 T. If it has a mass of 10 g, what is the minimum current through the wire that would cause a magnetic force equal to its weight?

2.0 A

Two resistors of values 6.0 and 12.0 W are connected in parallel. This combination in turn is hooked in series with a 4.0-W resistor and a 24-V battery. What is the current in the 6-W resistor?

2.0 A

Two resistors of values 6.0 and 12.0 W are connected in parallel. This combination in turn is hooked in series with a 2.0-W resistor and a 24-V battery. What is the current in the 2-W resistor?

2.0 A ? maybe 4.0 A

An electron is moving at a speed of 6.0 ´ 106 m/s at an angle of 30° with respect to a uniform magnetic field of 8.0 ´ 10-4 T. What is the radius of the resulting helical path? (me = 9.11 ´ 10-31 kg, qe = 1.6 ´ 10-19 C)

2.1 cm

Four 1.5-volt AA batteries in series power a transistor radio. If the batteries hold a total charge of 240 C, how long will they last if the radio has a resistance of 200 W?

2.2 h

The current in an electron beam in a cathode-ray tube is measured to be 70 µA. How many electrons hit the screen in 5.0 s? (e = 1.6 ´ 10-19 C)

2.2 x 10^15 electrons

What is the equivalent resistance for these 3.00-W resistors?

2.25 W

An electron with a speed of 2.0 ´ 106 m/s moves into a uniform electric field of 500 N/C that is parallel to the electron's motion. How long does it take to bring the electron to rest? (me = 9.11 ´ 10-31 kg, e = 1.6 ´ 10-19 C)

2.3 x 10^-8 s

A metallic object holds a charge of -3.8 ´ 10-6 C. What total number of electrons does this represent? (e = 1.6 ´ 10-19 C is the magnitude of the electronic charge.)

2.4 x 10^13

A circuit consists of a 10-mH coil, a 9.0-V battery, a parallel combination of a 12-W resistor and a 6.0-W resistor, and a switch, all in series. What is the time constant of this circuit?

2.5 x 10^-3 s

The wiring in a motor has resistance of 3.0 W and produces a back emf of 1.0 V when connected to a 9.0-V battery of negligible resistance. Find the current flow through the motor.

2.7 A

Three 8.0-W resistors are connected in parallel. What is their equivalent resistance?

2.7 W

If a metallic wire of cross sectional area 3.0 ´ 10-6 m2 carries a current of 6.0 A and has a mobile charge density of 4.24 ´ 1028 carriers/m3, what is the average drift velocity of the mobile charge carriers? (charge value = 1.6 ´ 10-19 C)

2.9 x 10^-4 m/s

An electron is sent at high speed toward a gold nucleus (charge +79e). What is the electrical force acting on the electron when it is 3.0 ´ 10-14 m away from the gold nucleus? (e = 1.6 ´ 10-19 C, ke = 8.99 ´ 109 N·m2/C2)

20 N

Carbon has a negative temperature coefficient of resistance of -0.5 ´ 10-3 (°C)-1. What temperature increase would result in a resistance decrease of 1% for a carbon resistor?

20 degrees C

A high-voltage power line 20 m above the ground carries a current of 2 000 A. What is the magnetic field due to the current directly underneath the power line? (µ0 = 4p ´ 10-7 T×m/A)

20 mT

Two point charges, separated by 1.5 cm, have charge values of +2.0 and -4.0 µC, respectively. Suppose we determine that 10 field lines radiate out from the +2.0-µC charge. If so, what might be inferred about the -4.0-µC charge with respect to field lines?

20 radiate in

A hair dryer draws 1 200 W, a curling iron draws 800 W, and an electric light fixture draws 500 W. If all three of these appliances are operating in parallel on a 120-V circuit, what is the total current drawn?

20.8 A

The following three appliances are connected to a 120-V house circuit: i) toaster, 1 200 W, ii) coffee pot, 750 W, and iii) microwave, 800 W. If all were operated at the same time, what total current would they draw?

23 A

What is the potential difference between points a and b?

24 V ? maybe 3.5 V

Three 8.0-W resistors are connected in series. What is their equivalent resistance?

24.0 W

A solenoid with 500 turns, 0.10 m long, carrying a current of 4.0 A and with a radius of 10-2 m will have what strength magnetic field at its center? (magnetic permeability in empty space µ0 = 4p ´ 10-7 T×m/A)

250 x 10^-4 T

A 20-W platinum wire at 20°C with a temperature coefficient of resistivity of 3.9 ´ 10-3 (°C)-1 will have what resistance at 100°C?

26 W

The two ends of a 3.0-W resistor are connected to a 9.0-V battery. What is the total power delivered by the battery to the circuit?

27 W

What is the self-inductance in a coil that experiences a 3.0-V induced emf when the current is changing at a rate of 110 A/s?

27 mH

When a voltage is generated by rotating a coil in a magnetic field at a constant rate, the period of the voltage equals the time that it takes for the coil to rotate through ____ radians.

2pi

Two cylindrical resistors are made of the same material and have the same resistance. The resistors, R1 and R2, have different radii, r1 and r2, and different lengths, L1 and L2. Which of the following relative values for radii and lengths would result in equal resistances?

2r1 = r2 and 4L1 = L2

By what factor is the self-inductance of an air solenoid changed if only its cross-sectional area, A, is tripled?

3

At the Fermilab accelerator in Weston, Illinois, singly-charged ions with momentum 4.8 ´ 10-16 kg×m/s are held in a circular orbit of radius 1 km by an upward magnetic field. What B-field must be used to maintain the ions in this orbit? (qion = 1.6 ´ 10-19 C)

3 T

A motor with a coil resistance of 10 W is attached to a voltage supply of 90 V. What is the current in the motor when it is running at its maximum speed with a back emf of 60 V?

3.0 A

The two ends of a 3.0-W resistor are connected to a 9.0-V battery. What is the current through the resistor?

3.0 A

Three 4.0-W resistors are connected in parallel to a 12.0-V battery. What is the current in any one of the resistors?

3.0 A

Two parallel wires are separated by 0.25 m. Wire A carries 5.0 A and Wire B carries 10 A, both currents in the same direction. The force on 0.80 m of Wire A is:

3.2 x 10^-5 N.

A flashlight bulb operating at a voltage of 4.5 V has a resistance of 8.0 W. How many electrons pass through the bulb filament per second (e = 1.6 ´ 10-19 C)?

3.5 x 10^18

An 8.00-W resistor is dissipating 100 watts. What are the current through it, and the difference of potential across it?

3.54 A, 28.3 V

A circuit contains a 6.0-V battery, a 4.0-W resistor, a 0.60-µF capacitor, an ammeter, and a switch in series. What will be the charge on the capacitor 10 min after the switch is closed?

3.6 uc

In a thundercloud there may be an electric charge of +40 C near the top of the cloud and -40 C near the bottom of the cloud. These charges are separated by about 2.0 km. What is the electric force between these two sets of charges? (ke = 8.99 ´ 109 N·m2/C2)

3.6 x 10^6 N

An air-core inductor has 1 000 turns/m and an internal volume of 3.0 cm3. What is its inductance?

3.8 mH

A proton is released such that it has an initial speed of 4.0 ´ 105 m/s from left to right across the page. A magnetic field of 1.2 T is present at an angle of 30° to the horizontal direction (or positive x axis). What is the magnitude of the force experienced by the proton? (qp = 1.6 ´ 10-19 C)

3.8 x 10^-14 N

A coil is rotated in a magnetic field generating an emf given by emf = NBAw sin q, where q = wt. At which angle q is the emf half of its maximum value?

30 degrees

If a 500-W heater carries a current of 4.00 A, what is the resistance of the heating element?

31.3 Q

Two point charges, separated by 1.5 cm, have charge values of +2.0 and -4.0 µC, respectively. What is the value of the mutual force between them? (ke = 8.99 ´ 109 N×m2/C2)

320 N

An electric clothes dryer draws 15 A at 220 V. If the clothes put into the dryer have a mass of 7.0 kg when wet and 4.0 kg dry, how long does it take to dry the clothes? (Assume all heat energy goes into vaporizing water, Lv = 2.26 ´ 106 J/kg.)

34 min

An airplane with a wingspan of 60.0 m flies parallel to the Earth's surface at a point where the downward component of the Earth's magnetic field is 0.400 ´ 10-4 T. If the induced potential between wingtips is 0.900 V, what is the plane's speed?

375 m/s

In the United States, the value of w for commercially generated power is ____ in SI units.

377

A superconducting solenoid is to be designed to generate a magnetic field of 5.00 T. If the solenoid winding has 1 000 turns/m, what is the required current? (µ0 = 4p ´ 10-7 T×m/A)

3980 A

**Two point charges are 4 cm apart. They are moved to a new separation of 2 cm. By what factor does the resulting mutual force between them change?

4

What is the current flowing through the 2-W resistor?

4 A

A closed surface contains the following point charges: 6 C, 4 C, -2 C, -4 C. The electric flux coming out of the surface is:

4 C/eo.

A spherical volume of space has an electric field of intensity 100 N/C directed radially outward from its surface of radius 0.600 m. What is the net charge enclosed within this surface?

4.0 nC

What is the stored energy in a 0.50-mH coil carrying a current of 4.0 A?

4.0 x 10^-3 J

Two electrons are separated by one cm. What is the ratio of the electric force to the gravitational force between them? (me = 9.11 ´ 10-31 kg, ke = 8.99 ´ 109 N×m2/C2, G = 6.67 ´ 10-11 N×m2/kg2, and e = 1.6 ´ 10-19 C)

4.2 x 10^42

A 12-V battery is connected in series with a switch, 6.0-W resistor and coil. What energy is stored in the coil when the current is 2.0 A? The time constant is 4.0 ´ 10-4 s.

4.8 x 10^-3 J

Charges of 4.0 µC and -6.0 µC are placed at two corners of an equilateral triangle with sides of 0.10 m. At the third corner, what is the electric field magnitude created by these two charges? (ke = 8.99 ´ 109 N·m2/C2)

4.8 x 10^6 N/C

A loop of area 0.250 m2 is in a uniform 0.020 0-T magnetic field. If the flux through the loop is 3.83 ´ 10-3 T·m2, what angle does the normal to the plane of the loop make with the direction of the magnetic field?

40.0 degree

A planar loop consisting of four turns of wire, each of which encloses 200 cm2, is oriented perpendicularly to a magnetic field that increases uniformly in magnitude from 10 mT to 25 mT in a time of 5.0 ms. What is the resulting induced current in the coil if the resistance of the coil is 5.0 W?

48 mA

A 10-V-emf battery is connected in series with the following: a 2-mF capacitor, a 2-W resistor, an ammeter, and a switch, initially open; a voltmeter is connected in parallel across the capacitor. After the switch has been closed for a relatively long period (several seconds, say), what are the current and capacitor voltage readings, respectively?

5 A, zero V ? maybe 0 A, zero V

An RL series circuit has the following components: 5.0-mH coil, 1.0-W resistor, 12-V battery, ammeter and switch. What is the time constant of this circuit?

5.0 x 10^-3 s

A metal wire has a resistance of 25.00 W under room temperature conditions of 25°C. When the wire is heated to 85°C the resistance increases by 0.75 W. What is the temperature coefficient of resistivity of this metal?

5.0 x 10^-4 (°C)-1

A 0.20-m-long metal rod has a radius of 1.0 cm and a resistance of 3.2 ´ 10-5 W. What is the resistivity of the metal?

5.0 x 10^-8 W×m

You measure a 25.0-V potential difference across a 5.00-W resistor. What is the current flowing through it?

5.00 A

The average distance of the electron from the proton in the hydrogen atom is 0.51 ´ 10-10 m. What is the electric field from the proton's charge at the location of the electron? (ke = 8.99 ´ 109 N×m2/C2, e = 1.6 ´ 10-19 C)

5.5 x 10^11 N/C

A circuit consists of a 10-mH coil, a 12-W resistor, a 6.0-W resistor, a 9.0-V battery and a switch, all in series. What is the time constant of this circuit?

5.6 x 10^-4 s

When a 24.0-W resistor is connected across a 12.0-V battery, a current of 482 mA flows. What is the power output delivered by the emf of the battery?

5.78 W

An electric car is designed to run off a bank of 12-V batteries with total energy storage of 3.0 ´ 107 J. If the electric motor draws 6 000 W in moving the car at a steady speed of 10 m/s, how far will the car go before it is "out of juice?"

50 km

An RL circuit has L = 0.40 H and R = 5.0 W. It is connected to a battery with e = 22 V at time t = 0. Find the energy stored in the inductor when the current in the circuit is 0.50 A

50 mJ

An electric car is designed to run off a bank of 12-V batteries with total energy storage of 3.0 ´ 107 J. If the electric motor draws 6 000 W, what current will be delivered to the motor?

500 A

A flat coil of wire consisting of 20 turns, each with an area of 50 cm2, is positioned perpendicularly to a uniform magnetic field that increases its magnitude at a constant rate from 2.0 T to 6.0 T in 2.0 s. If the coil has a total resistance of 0.40 W, what is the magnitude of the induced current

500 mA

Consider the circuit shown in the figure. What power is dissipated by the entire circuit?

52 W

A large jetliner with a wingspan of 40 m flies horizontally and due north at a speed of 300 m/s in a region where the magnetic field of the earth is 60 µT directed 50° below the horizontal. What is the magnitude of the induced emf between the ends of the wing?

550 mV

What is the maximum number of 60-W light bulbs you can connect in parallel in a 120-V home circuit without tripping the 30-A circuit breaker?

59

A series RC circuit, which is made from a battery, a switch, a resistor, and a 3.0-mF capacitor, has a time constant of 9.0 ms. If an additional 6.0-mF is added in series to the 3.0-mF capacitor, what is the resulting time constant?

6.0 ms

Some superconductors are capable of carrying a very large quantity of current. If the measured current is 1.00 ´ 105 A, how many electrons are moving through the superconductor per second? (e = 1.60 ´ 10-19 C)

6.25 x 10^23

How much power is being dissipated by one of the 10-W resistors?

6.4 W

An electron with a charge value of 1.6 ´ 10-19 C is moving in the presence of an electric field of 400 N/C. What force does the electron experience?

6.4 x 10^-17 N

A 6.00 mC charge is placed at the origin and a second charge is placed on the x-axis at x = 0.300 m. If the resulting force on the second charge is 6.40 N in the positive x-direction, what is the force on the charge at the origin?

6.40 N in the negative x-direction

The heating coil of a hot water heater has a resistance of 20 W and operates at 210 V. How long a time is required to raise the temperature of 200 kg of water from 15°C to 80°C? (The specific heat for water = 103 cal/kg×°C and 1.0 cal = 4.186 J.)

6.9 h

An incredible amount of electrical energy passes down the funnel of a large tornado every second. Measurements taken in Oklahoma at a distance of 9.00 km from a large tornado showed an almost constant magnetic field of 1.50 ´ 10-8 T associated with the tornado. What was the average current going down the funnel? (µ0 = 4p ´ 10-7 T×m/A

675 A

Superconductors have been discussed as a means for electrical energy storage. Because they are resistanceless, a current once started in a loop would continue without loss. If a current of 1.0 x 104 A were started in a huge toroidal coil of radius 1.0 km and inductance 50 H, how much electrical energy (in kWh) could be stored?

690 kWh

What is the minimum frequency with which a 200-turn, flat coil of cross sectional area 300 cm2 can be rotated in a uniform 30-mT magnetic field if the maximum value of the induced emf is to equal 8.0 V?

7.1 Hz

How long is a wire made from 100 cm3 of copper if its resistance is 8.5 ohms? The resistivity of copper is 1.7 x 10-5 W·m.

7.1 m

A proton moving at 3.0 ´ 104 m/s is projected at an angle of 30° above a horizontal plane. If an electric field of 400 N/C is acting down, how long does it take the proton to return to the horizontal plane? (Hint: Ignore gravity. mproton = 1.67 ´ 10-27 kg, qproton = 1.6 ´ 10-19 C)

7.8 x 10^-7 s

A high-voltage transmission line carries 1 000 A at 700 000 V. What is the power carried by the line

700 MW

An airplane is flying through a thundercloud at a height of 2 000 m. (This is a very dangerous thing to do because of updrafts, turbulence, and the possibility of electric discharge.) If there is a charge concentration of +40 C at height 3 000 m within the cloud and -40 C at height 1 000 m, what is the magnitude of the electric field E at the aircraft? (ke = 8.99 ´ 109 N·m2/C2)

720 000 N/C

A motor has an internal resistance of 12 W. When running, the motor has a back emf of 30 V and draws a current of 4.0 A. What is the supply voltage in this case?

78 V

In a certain material there is a current of 16 A flowing through a surface to the right, and there is an equal amount of positive and negative charge passing through the surface producing the current. How much negative charge passes through the surface?

8 C/s toward the left

A high voltage transmission line of diameter 2 cm and length 200 km carries a steady current of 1 000 A. If the conductor is copper with a free charge density of 8 ´ 1028 electrons/m3, how long does it take one electron to travel the full length of the cable? (e = 1.6 ´ 10-19 C)

8 x 10^8 s

If I1 goes to the right through R1, I2 goes to the right through R2, and I3 goes to the right through R3, what is the resulting equation resulting from applying Kirchhoff's loop rule for a clockwise loop around the perimeter of the circuit?

8.0 V + I1R1 + I3R3 = 0 ?

Two resistors of values 6.0 and 12.0 W are connected in parallel. This combination in turn is hooked in series with a 4.0-W resistor. What is the overall resistance of this combination?

8.0 W

A rectangular coil (0.20 m ´ 0.80 m) has 200 turns and is in a uniform magnetic field of 0.30 T. If the orientation of the coil is varied through all possible positions, the maximum torque on the coil by magnetic forces is 0.080 N×m. What is the current in the coil?

8.3 mA

A proton, mass 1.67 ´ 10-27 kg and charge +1.6 ´ 10-19 C, moves in a circular orbit perpendicular to a uniform magnetic field of 0.75 T. Find the time for the proton to make one complete circular orbit.

8.7 x 10^-8 s

In Millikan's oil drop experiment, if the electric field between the plates was of just the right magnitude, it would exactly balance the weight of the drop. Suppose a tiny spherical oil droplet of radius 1.6 ´ 104 cm carries a charge equivalent to one electron. What electric field is required to balance the weight? (The density of oil is 0.85 g/cm3, e = 1.6 ´ 10-19 C.)

8.9 x 10^5 N/C

A water pump draws about 3.8 A when connected to 240 V. What is the cost (with electrical energy at 9 cents per kWh) of running the pump for 10 h?q

82 cents

If electrical energy costs 5.5 cents per kWh, what does it cost to heat 200 kg water from 15°C to 80°C? (The specific heat of water = 103 cal/kg×°C and 1.0 cal = 4.186 J.)

83 cents

A light bulb, sold as long-lasting, is rated 100 W at 130 V. The "increased" lifetime comes from using it at 120 V. Assuming negligible change in resistance at the different voltage, what is its power consumption at 120 V?

85 W

By what factor is the self-inductance of an air solenoid changed if only its number of coil turns, N, is tripled?

9

By what factor is the self-inductance of an air solenoid changed if its length and number of coil turns are both tripled?

9 ? maybe 3

If a 9.0-V battery, with negligible internal resistance, and an 18-W resistor are connected in series, what is the amount of electrical energy transformed to heat per coulomb of charge that flows through the circuit?

9.0 J

A 6.0 mC charge is placed at the origin and a second charge is placed on the x-axis at x = 0.30 m. If the resulting force on the second charge is 5.4 N in the positive x-direction, what is the value of its charge?

9.0 nC ?

We have an initially uncharged hollow metallic sphere with radius of 5.0 cm. I place a small object with a charge of +10 µC at the center of the sphere through a hole in the surface. Find the electric field present at a point 10 cm from the sphere's center. (ke = 8.99 ´ 109 N×m2/C2)

9.0 x 10^6 N/C

A proton, which moves perpendicular to a magnetic field of 1.2 T in a circular path of radius 0.080 m, has what speed? (qp = 1.6 ´ 10-19 C and mp = 1.67 ´ 10-27 kg)

9.2 x 10^6 m/s

A metal wire has a resistance of 10.00 W at a temperature of 20°C. If the same wire has a resistance of 10.55 W at 90°C, what is the resistance when its temperature is -20°C?

9.69 W

The force on a charged particle created by its motion in a magnetic field is maximum at what angle between the particle velocity and field?

90 degrees

When current is flowing in a superconductor, which statement is not true?

A battery is needed to keep the current going

The size of the electric current in an electrical conductor is a function of which of the following?

All of the above choices are valid

How can a charged object attract an uncharged object made of non-conducting material?

Attraction of an insulator is not possible ?

Charge A has 10 electric field lines coming out, Charge B has 20 lines coming out, and Charge C has 30 lines coming in. Which pair of these charges will have the largest force between them if placed one cm apart?

B and C

The direction of the force on a current carrying wire located in an external magnetic field is which of the following?

Both choices A and B are valid.

The basic function of an electromotive force in a circuit is to do which of the following?

Convert some other form of energy into electrical

Three resistors connected in series have individual voltages labeled DV1, DV2 and DV3, respectively. Which of the following expresses the value of the total voltage DVT taken over the three resistors together?

DVT = DV1 + DV2 + DV3

Three resistors connected in parallel have the individual voltages labeled DV1, DV2 and DV3, respectively. Which of the following expresses the total voltage DVT across the three resistors when connected in this manner?

DVT = DV1 = DV2 = DV3

A proton with initial kinetic energy E is moving in circular motion in a uniform magnetic field. When it has completed one eighth of a revolution, what is its kinetic energy?

E

Magnetism had been a known phenomenon for some time before its relation to electric currents was found. That a current in a wire produces a magnetic field was discovered by:

Faraday ? maybe Oersted

If I1 goes to the right through R1, I2 goes to the right through R2, and I3 goes to the right through R3, what is the resulting equation resulting from applying Kirchhoff's junction rule at point b?

I1 + I2 + I3 = 0

What is Kirchhoff's 1st equation for this junction?

I1 + I2 + I3 = 0

Three resistors connected in series each carry currents labeled I1, I2 and I3. Which of the following expresses the value of the total current IT in the system made up of the three resistors in series?

IT = I1 = I2 = I3

Three resistors connected in parallel each carry currents labeled I1, I2 and I3. Which of the following expresses the value of the total current IT in the combined system?

IT = I1 = I2 = I3 ? maybe IT= I1+I2+I3

Household 120-V outlets are made to accept three-pronged plugs. One of the prongs attaches to the "live" wire at 120 V, and another attaches to the "neutral" wire that is connected to ground. What is the round third prong for?

It connects the case of the appliance directly to ground for safety purposes.

When a light bulb is turned on, its resistance increases until it reaches operating temperature. What happens to the current in the bulb as it is warming up?

It decreases at first and then increases. ? maybe it decreases

A resistor is made of a material that has a resistivity that is proportional to the current going through it. If the voltage across the resistor is doubled, what happens to the current through it?

It increases by a factor of 2^1/2

A resistor is made of a material that has a resistivity that is proportional to the current going through it. If the voltage across the resistor is doubled, what happens to the power dissipated by it?

It increases by a factor of 2^3/2.

A soft magnetic material has which property?

It is easy to magnetize

If the current in a wire is tripled, what effect does this have on the electron drift velocity in the wire?

It triples.

The quantity volt is equivalent to which of the following?

J/C

Two wires with the same resistance have the same diameter but different lengths. If wire 1 has length L1 and wire 2 has length L2, how do L1 and L2 compare if wire 1 is made from copper and wire 2 is made from aluminum? The resistivity of copper is 1.7 ´ 10-5 W·m and the resistivity of aluminum is 2.82´ 10-5 W·m.

L1 = 1.7 L2

The principle or law that says "an induced emf in a circuit loop produces a current whose magnetic field opposes further change of magnetic flux" is credited to:

Lenz

Who was the first to determine the electron's charge?

Millikan

**Electric field is dimensionally equivalent to which of the following?

N/C

The number density of conduction electrons in a metal can be found from the density r of the metal, the mass per mole M of the metal, the number of conduction electrons per metal atom, and Avogadro's number NA. If we assume one conduction electron per atom, which of the following gives the number density of conduction electrons for a given metal?

NAr /M

The constant ke, which appears in Coulomb's law formula, is equivalent dimensionally to which of the following?

N×m^2/C^2

Superconductivity was discovered by:

Onnes

**Doug rubs a piece of fur on a hard rubber rod, giving the rod a negative charge. What happens?

Protons are removed from the rod ?

Three resistors, each with resistance R1, are in parallel in a circuit. They are replaced by one equivalent resistor, R. Compare this resistor to the first resistor of the initial circuit. Which of the following statements is true?

R is less than R1. ? maybe the voltage across R equals the voltage across R1

If R1 < R2 < R3, and if these resistors are connected in parallel in a circuit, which one has the highest current?

R1

Which two resistors are in parallel with each other?

R2 and R3

If R1 < R2 < R3, and if these resistors are connected in series in a circuit, which one dissipates the greatest power?

R3

Which resistor is in series with resistor R?

R4

Three resistors with values of R1, R2 and R3, respectively, are connected in series. Which of the following expresses the total resistance, RT, of the three resistors?

RT = R1 + R2 + R3

Three resistors with values R1, R2 and R3, respectively, are connected in parallel. Which of the following expresses the total resistance, RT, of the three resistors when connected in parallel?

RT = R1 + R2 + R3 ? maybe RT = (1/R1 + 1/R2 + 1/R3)-1

I wish to use a positively charged rod to charge a ball by induction. Which statement is correct?

The ball must be a conductor

Three resistors, each with resistance R1, are in series in a circuit. They are replaced by one equivalent resistor, R. Comparing this resistor to the first resistor of the initial circuit, which of the following is true?

The current through R equals the current through R1.

A coil is placed in a changing magnetic field and an emf is induced. What happens to the induced emf if the rate of change of magnetic field quadruples

The emf quadruples.

Two insulated current-carrying straight wires of equal length are arranged in the lab so that Wire A carries a current northward and Wire B carries a current eastward, the wires crossing at their midpoints separated only by their insulation. Which of the following statements are true?

There are forces, but the net force on each wire is zero

The unit of electric resistance, the ohm, is equivalent to which of the following?

V/A

Two charges, +Q and -Q, are located two meters apart and there is a point along the line that is equidistant from the two charges as indicated. Which vector best represents the direction of the electric field at that point?

Vector EA (pointing to the -Q charge)

The unit of inductance, the henry, is equivalent to:

V·s/A.

The unit for rate of energy transformation, the watt, in an electric circuit is equivalent to which of the following?

V×A

A proton moving with a speed of 3.0 ´ 105 m/s perpendicular to a uniform magnetic field of 0.20 T will follow which of the paths described below? (qp = 1.6 ´ 10-19 C and mp = 1.67 ´ 10-27 kg)

a circular path of 1.6 cm radius

A deuteron, with the same charge but twice the mass of a proton, moves with a speed of 3.0 ´ 105 m/s perpendicular to a uniform magnetic field of 0.20 T. Which of the paths described below would it follow? (qp = 1.6 ´ 10-19 C and md = 3.34 ´ 10-27 kg)

a circular path of 3.1 cm radius

Electrical charges and magnetic poles have many similarities, but one difference is

a magnetic pole cannot be isolated

The magnetic pole of the Earth nearest the geographic North Pole corresponds to which of the following

a magnetic south pole

Two parallel conductors are carrying currents in the same direction. The currents are non-zero and not necessarily equal. The magnitude of the magnetic field midway between them is 40 mT. If one of the currents then has its direction reversed, what is the resulting magnitude of the magnetic field midway between them?

a value greater than 40 mT

Two parallel conductors are carrying currents in the opposite direction. The currents are non-zero and not necessarily equal. The magnitude of the magnetic field midway between them is 40 mT. If one of the currents then has its direction reversed, what is the resulting magnitude of the magnetic field midway between them?

a value greater than 40 mT ? maybe so magnetic field decreases compared to previous case

The term magnetic declination refers to which of the following?

angle between directions to true north and magnetic north

If a charged particle is moving in a uniform magnetic field, its path can be:

any of the above

An inductor, battery, resistance, and ammeter and switch are connected in series. If the switch, initially open, is now closed, what is the current's final value?

battery voltage divided by resistance

The force exerted on a current-carrying wire located in an external magnetic field is directly proportional to which of the following?

both A and B

Which of the following devices makes use of an electromagnet?

both A and B

A current in a solenoid with N turns creates a magnetic field at the center of that loop. The field strength is directly proportional to:

both choices A and B

A repelling force must occur between two charged objects under which conditions?

charges are of like signs

Which of the following best characterizes electrical insulators?

charges on the surface don`t move

A bar magnet is falling through a loop of wire with constant velocity. The north pole enters first. As the south pole leaves the loop of wire, the induced current (as viewed from above) will be:

clockwise

A bar magnet is falling through a loop of wire with constant velocity. The south pole enters first. As the magnet leaves the wire, the induced current (as viewed from above):

clockwise ? maybe counterclockwise

The dip angle is:

close to or at zero near the equator.

Geophysicists today generally attribute the existence of the Earth's magnetic field to which of the following?

convection currents within the liquid interior

In the Millikan oil-drop experiment it was found that oil droplets:

could only have negative net charge ?

The magnetic field of the Earth is believed responsible for which of the following

deflection of charged cosmic rays

The combination of two separated point charges of opposite sign but equal magnitude is called an electric:

dipole

How is the energy stored in a current-carrying inductor related to the current value, I?

directly proportional to I^2

How is the energy stored in a current-carrying inductor related to its self-inductance, L?

directly proportional to L

A circular current loop is placed in an external magnetic field. How is the torque related to the radius of the loop?

directly proportional to radius squared

Which process will double the power given off by a resistor?

doubling the current by making a resistance half as big

A wire is lying horizontally in the north-south direction and the horizontal magnetic field is toward the east. Some positive charges in the wire move north and an equal number of negative charges move south. The direction of the force on the wire will be:

down, into the page

When a superconductor's temperature drops below the critical temperature, its resistance:

drops to zero

If a proton is released at the equator and falls toward the Earth under the influence of gravity, the magnetic force on the proton will be toward the:

east

Which of the following best characterizes electrical conductors?

electric charges move freely

The beam of electrons that hits the screen of an oscilloscope is moved up and down by:

electrical charges on deflecting plates.

The function of the electric motor is which one of the following conversion processes?

electrical energy to mechanical

**When a glass rod is rubbed with silk, which of the following statements best describes what happens?

electrons are removed from the rod

If the induced current in a wire loop were such that the flux it produces were in the same direction as the change in external flux causing the current, which of the following conservation laws would end up being violated?

energy

The current in a long wire creates a magnetic field in the region around the wire. How is the strength of the field at distance r from the wire center related to the magnitude of the field?

field inversely proportional to r

The number of electric field lines passing through a unit cross sectional area is indicative of:

field strength

A current in a long, straight wire produces a magnetic field. The magnetic field lines:

form circles that go around the wire

The right-hand rule allows one to find a property of the interaction of a magnetic field with a charged particle. The right-hand rule applied to moving charges:

gives the direction of the force on a charge moving in a magnetic field.

"GFI" stands for:

ground fault interrupter.

In applications where electrical shocks may be more likely, such as around water in kitchens and bathrooms, special outlets called GFI's are used. What does GFI stand for?

ground-fault interrupter

Ten coulombs of charge start from the negative terminal of a battery, flow through the battery and then leave the positive terminal through a wire, flow through a resistor and then return to the starting point on this closed circuit. In this complete process, the ten coulombs:

have no net change in potential energy

The operation of a tape player to play music depends on which of the following?

induced current from the motion of a magnet past a wire

The internal resistances of an ideal voltmeter and an ideal ammeter are respectively (ideal meaning the behavior of the system is not changed when using the meter):

infinite and zero

A proton is released such that its initial velocity is from right to left across this page. The proton's path, however, is deflected in a direction toward the bottom edge of the page due to the presence of a uniform magnetic field. What is the direction of this field?

into the page

Of the following substances, which one contains the highest density of free electrons?

iron

The magnet moving past an object will produce eddy currents in the object if the object:

is a conductor

The "back emf" of a motor refers to a source of voltage that

is biggest when the motor turns fastest.

The resistivity of a material is doubled when heated a certain amount. What happens to the resistance of a resistor made of this material when heated the same amount

it doubles

When an electromagnet has an iron core inserted, what happens to the strength of the magnet?

it increases

In a mass spectrometer, an ion will have a smaller radius for its circular path if:

its charge is greater.

Which is a unit of power?

kWh ?

The basic function of the electric generator is which of the following conversion processes?

mechanical energy to electrical

When a magnetic field causes a charged particle to move in a circular path, the only quantity listed below which the magnetic force changes significantly as the particle goes around in a circle is the particle's:

momentum

The back emf in an electric motor is its maximum value under which condition?

motor speed is a maximum

There is a magnetic force on a particle. It is possible that the particle is:

moving in the direction of the magnetic field. ?

If body M, with a positive charge, is used to charge body N by induction, what will be the nature of the charge left on the latter?

must be negative

When an electric current exists within a conducting wire, which of the following statements describes the condition of any accompanying electric field?

must be parallel to current flow

**If body P, with a positive charge, is placed in contact with body Q (initially uncharged), what will be the nature of the charge left on Q?

must be positive

A coil is placed in a magnetic field and has a flux FB through it. The coil is stressed so that its area reduces to 75% of its original value. If the plane of the coil stays the same and the flux through it remains the same, how must the magnetic field change?

must increase by 33%

Which of the following is not a hard magnetic material?

neodymium ? maybe iron

A superconducting wire's chief characteristic is which of the following?

no resistance

A certain capacitor is charged to 10 V and then, at t = 0, allowed to discharge through a certain resistor. There will be a certain time before the voltage across the capacitor reaches 5 V. This time can be decreased for this circuit by increasing:

none of the above

Consider some material that has been cooled until it has become a superconductor. If it is cooled even further its resistance will:

none of the above

Two identical balls have the same amount of charge, but the charge on ball A is positive and the charge on ball B is negative. The balls are placed on a smooth, level, frictionless table whose top is an insulator. Which of the following is true?

none of the above is correct

If a certain resistor obeys Ohm's law, its resistance will change:

none of the above, since resistance is a constant for the given resistor

The magnetic field going through a stationary circular loop increases from zero to 5 T in a certain time t. The induced current in the loop will depend on the radius of the loop, r, the resistance of the loop, R, and the time, t. If two of these stay constant, the induced current can be directly proportional to

none of these

Materials having resistance changes as voltage or current varies are called:

nonohmic.

A straight wire of length is oriented east-west and is in a magnetic field B pointing north. The wire is moving downward at a constant speed v. If the resistance of the rod is R, what is the current through the rod?

not given

The self-inductance of a solenoid increases under which of the following conditions?

only the number of coils is increased

According to Lenz's law the direction of an induced current in a conductor will be that which tends to produce which of the following effects?

oppose the effect which produces it

A proton moves across the Earth's equator in a northeasterly direction. At this point the Earth's magnetic field has a direction due north and is parallel to the surface. What is the direction of the force acting on the proton at this instant?

out of the Earth's surface

A horizontal wire of length 3.0 m carries a current of 6.0 A and is oriented so that the current direction is 50° S of W. The Earth's magnetic field is due north at this point and has a strength of 0.14 ´ 10-4 T. What is the direction of the force on the wire?

out of the Earth's surface ? maybe Thus, the net magnetic force that acts on the square loop is zero

Household circuits are wired in ___

parallel

**The electric field at the surface of a positively charged conductor has a direction characterized by which of the following?

perpendicular outward and away from the charge

An uncharged conductor is supported by an insulating stand. I pass a positively charged rod near the left end of the conductor, but do not touch it. The right end of the conductor will be:

positive

**The electric field of a point charge has an inverse ____ behavior

r^2

The magnetic domains in a non-magnetized piece of iron are characterized by which orientation?

random

Two parallel conductors each of 0.50 m length, separated by 5.0 ´ 10-3 m and carrying 3.0 A in opposite directions, will experience what type and magnitude of mutual force? (magnetic permeability in empty space µ0 = 4p ´ 10-7 T×m/A)

repulsive, 1.8 x 10^-4 N

The temperature coefficient of resistivity is a quantity that is:

sometimes negative

Two loops of wire are arranged so that a changing current in one will induce a current in the other. If the current in the first is increasing clockwise by 1.0 A every second, the induced current in the second loop will:

stay constant

A charge, +Q, is placed inside a balloon and the balloon is inflated. As the radius of the balloon r increases the number of field lines going through the surface of the balloon:

stays the same

The path of a charged particle moving parallel to a uniform magnetic field will be a:

straight line

In a circuit made up of inductor, resistance, ammeter, battery and switch in series, at which of the following times after the switch is closed is the rate of current increase greatest?

ten time constant ? maybe zero

In a circuit made up of inductor L, resistance R, ammeter, battery and switch in series, the current is greatest at which of the following times, as measured after the switch is closed?

ten times constant

Resistors of values 8.0 W, 12.0 W, and 24.0 W are connected in series across a battery with a small internal resistance. Which resistor dissipates the greatest power?

the 24.0-W resistor

Resistors of values 8.0 W, 12.0 W, and 24.0 W are connected in parallel across a fresh battery. Which resistor dissipates the greatest power?

the 8.0-W resistor

Which of the following locations has the smallest (in magnitude) magnetic declination?

the South Carolina - Georgia border

A light bulb with a tungsten filament is attached to a source of variable voltage. As the voltage is increased on the bulb,

the bulb's resistance increases

A current in a solenoid coil creates a magnetic field inside that coil. The field strength is directly proportional to:

the current

A straight wire of length is oriented east-west and is in a magnetic field B pointing north. The wire is moving downward at a constant speed v. Which end of the rod is positively charged?

the east end

If a conductor is in electrostatic equilibrium near an electrical charge:

the electric field inside the conductor must be zero.

The Millikan oil-drop experiment demonstrated that:

the electronic charge is quantized.

The operation of an electric motor depends on which of the following effects?

the force acting on a current-carrying wire in a magnetic field

If a charge +Q is placed inside a hollow isolated conductor that is originally neutral and the charge does not touch that conductor at any time:

the inside surface of the conductor will become positively charged ?

A bar magnet is falling through a loop of wire with constant velocity. The north pole enters first. The induced current will be greatest in magnitude when the magnet is located so that:

the loop is near either the north or the south pole.

If a bar magnet is falling through a loop of wire, the induced current in the loop of wire sets up a field which exerts a force on the magnet. This force between the magnet and the loop will be attractive when:

the magnet is leaving the loop.

Electricity may be generated by rotating a loop of wire between the poles of a magnet. The induced current is greatest when

the plane of the loop is parallel to the magnetic field.

A metal rod is falling toward the surface of the Earth near the equator. As it falls, one end of the rod becomes positively charged due to the motional emf of the rod through the Earth's magnetic field. The rod is oriented so that

the rod is horizontal with the positive end toward the east.

Relative distribution of charge density on the surface of a conducting solid depends on:

the shape of the conductor.

When you flip a switch to turn on a light, the delay before the light turns on is determined by:

the speed of the electric field moving in the wire

The electric field associated with a uniformly charged hollow metallic sphere is the greatest at:

the sphere's outer surface.

Consider two long, straight parallel wires, each carrying a current I. If the currents are flowing in opposite directions:

the two wires will repel each other.

Which voltage is not caused by a source of emf?

the voltage across a charged capacitor

A sensitive ammeter is connected to a wire loop and placed within the magnetic field of a strong horseshoe magnet. The ammeter shows a deflection when:

the wire is moved parallel to the field. ? maybe perpendicularly

A stationary positive charge +Q is located in a magnetic field B, which is directed toward the right as indicated. The direction of the magnetic force on Q is

there is no magnetic force

When charging two objects by rubbing them together:

they must be made of different material

If one doubles the emfs in a circuit and doubles the resistances in the circuit at the same time, what happens to the currents through the resistors? Assume there are only emfs and resistors in the circuit.

they stay the same

Assume that a uniform magnetic field is directed into this page. If an electron is released with an initial velocity directed from the bottom edge to the top edge of the page, which of the following describes the direction of the resultant force acting on the electron?

to the left ?

Two parallel wires are separated by 0.25 m. Wire A carries 5.0 A and Wire B carries 10 A, both currents in the same direction. The force on 0.80 m of Wire A is:

toward Wire B.

The unit of electric current, the ampere, is equivalent to which of the following?

v/w

Wire A and Wire B are each carrying the same current. If the diameter of Wire A is twice that of Wire B, how does the drift velocity vdA in Wire A compare to that in Wire B?

vdA = vdB /4

Which is not a force?

voltage

The units T·m2/s are equivalent to:

webers ?

At what point is the charge per unit area greatest on the surface of an irregularly shaped conducting solid?

where curvature is greatest

Two long parallel wires 20 cm apart carry currents of 5.0 A and 8.0 A in the same direction. Is there any point between the two wires where the magnetic field is zero?

yes, 7.7 cm from the 5-A wire

A 2.0-m wire segment carrying a current of 0.60 A oriented parallel to a uniform magnetic field of 0.50 T experiences a force of what magnitude?

zero

A 500-turn circular coil with an area of 0.050 0 m2 is mounted on a rotating frame, which turns at a rate of 20.0 rad/s in the presence of a 0.050 0-T uniform magnetic field that is perpendicular to the axis of rotation. What is the instantaneous emf in the coil at the moment that the normal to its plane is parallel to the field?

zero

A circular loop (area = 0.20 m2) turns in a uniform magnetic field with B = 0.13 T. At an instant when the angle between the magnetic field and the normal to the plane of the loop is p rads and is decreasing at the rate of 0.50 rad/s, what is the magnitude of the emf induced in the loop?

zero

An electron which moves with a speed of 3.0 ´ 104 m/s parallel to a uniform magnetic field of 0.40 T experiences a force of what magnitude? (e = 1.6 ´ 10-19 C)

zero

The temperature coefficient of resistivity for a "perfect" ohmic material would be

zero

There is a current I flowing in a clockwise direction in a square loop of wire that is in the plane of the paper. If the magnetic field B is toward the right, and if each side of the loop has length L, then the net magnetic force acting on the loop is:

zero

Two point charges each have a value of 30.0 mC and are separated by a distance of 4.00 cm. What is the electric field midway between the two charges? (ke = 8.99 ´ 109 N·m2/C2)

zero

A 0.200-m wire is moved parallel to a 0.500-T magnetic field at a speed of 1.50 m/s. What emf is induced across the ends of the wire?

zero ?

Two loops of wire are arranged so that a changing current in one, the primary, will induce a current in the other, the secondary. The secondary loop has twice as many turns as the primary loop. The current in the primary at this moment is 3 A and increasing. The current in the secondary must be

zero ? maybe 1.5 A

There is a current I flowing in a clockwise direction in a square loop of wire that is in the plane of the paper. If the magnetic field B is toward the right, and if each side of the loop has length L, then the net magnetic torque acting on the loop is

zero ? maybe IBL^2

A 10-V-emf battery is connected in series with the following: a 2-µF capacitor, a 2-W resistor, an ammeter, and a switch, initially open; a voltmeter is connected in parallel across the capacitor. At the instant the switch is closed, what are the current and capacitor voltage readings, respectively?

zero A, zero V ? maybe 5A, zero V