PHYS 222 Exam 1

7.7

681 J of work are required to carry a 89 C charge from point 1 to point 2. What is the magnitude if the potential difference between point 1 and point 2 in units of V? Enter a number with one digit behind the decimal point.

91.34

A 97 microCoulomb charge is located at the origin and a -27 microCoulomb charge is located on the y-axis at y = 50.8 cm. What is the magnitude of the force with which the charges attract each other in units of N? Enter a number with two digits behind the decimal point.

the whole bird is at approximately the same potential, so there is no electric field across it

A bird sits on a high-voltage line. Why does the bird not get hurt? Birds are not affected by electric fields. The whole bird is at approximately the same potential, so there is no electric field across it. The bird is very small, and therefore can hold only a small amount of charge. The bird's charge is opposite to that of the line, and the charges cancel out. The bird is very lucky.

(c)

A bulb (i.e., a resistor) is connected in series to a switch, a battery, and an uncharged capacitor. At t = 0, the switch is closed. Which of the following best describes the brightness of the bulb as a function of time? (a) (b) (c) (d) The current is constant since the battery voltage is constant.

1.05

A capacitor with a charge of 4.1 C has its terminals shorted by a metal wire so that the charge flows off within 3.9 s. What is the average current flowing during that time in Ampere (A)? Enter a numnber with two digits behind the decimal point.

the author of the textbook made a mistake

A certain physics textbook shows a region of space in which two electric field lines cross each other. We should conclude that at least two point charges are present. an electrical conductor is present. an insulator is present. the field points in two directions at the same place. the author of the textbook made a mistake.

3.42

A cosmic ray electron (m = 9.1*10-31 kg) moves at 5.17*106 m/s perpendicular to the Earth's magnetic field at an altitude where field strength is 0.86*10-5 T. What is the radius r (in m) of the circular path the electron follows? Enter anumber with two digits behind the decimal point.

4847.5

A cube with sides of area 92 cm2 contains a 42.9 nanoCoulomb charge. Find the flux of the electric field through the surface of the cube in unis of Nm2/C. Enter a number with one digit behind the decimal point.

form circles that go around the wire

A current in a long, straight wire produces a magnetic field. The magnetic field lines go out from the wire to infinity. come in from infinity to the wire. form circles that pass through the wire. form circles that go around the wire. are parallel to the wire.

98.4

A current of 5.7 A flows through the heating element of heater converting 561 J of electrical energy into thermal energy every second. What is the voltage (in V) across the ends of the heating element? Enter a number with one digit behind the decimal point.

3.3

A high voltage transmission line has an aluminum cable of diameter 4.8 cm and is 214 km long. The resistivity of Aluminum is 2.8*10-8 Ωm. What is the resistance of this cable in Ω? Enter a number with one digit behind the decimal point.

D

A negatively charged balloon is attracted to a neutral wooden cabinet due to polarization. Which one of the following diagrams best depict why this occurs?

each of the individual resistances is greater than 2 Ohm

A parallel combination of resistors has an equivalent (or effective) resistance of 2 Ω. Which one of the following is true? The sum of the individual resistances is 2 Ω. The sum of the reciprocals of the individual resistances is 2 Ω. Each of the individual resistances is greater than 2 Ω. Each of the individual resistances is smaller than 2 Ω. None of the above is true.

into the page

A positive charge is moving with velocity v in a region with magnetic field B. What is the direction of the force on the particle? opposite the direction of v in the direction of v into the page out of the page There is no force on the particle.

F is the same at all locations, but not zero

A positive charge is placed at one of 3 locations in a region where the electric field is uniform. Compare the magnitude F of the electric force on the charge at the different locations. F is greatest at location 1. F is greatest at location 2. F is greatest at location 3. F is the same at all locations, but not zero. F is zero at all locations.

east

A proton is released near the equator and falls toward the earth under the influence of gravity. The magnetic force on the proton will be toward the east. west. north. south. The magnetic force will be zero.

r = 0 (center of the sphere)

A solid, conducting sphere of radius R is positively charged. Of the following distances from the center of the sphere, which location will have the greatest electric potential? (Take V = 0 at r = infinity.) r = 0 (center of the sphere) r = 1.1 R. r = 1.25 R. r = 2 R. None of the above because the potential is constant.

the magnetic force will be zero

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 towards the right. towards the left. up. down. The magnetic force will be zero.

3979 A

A superconducting solenoid (coil) is used to generate a magnetic field of 10 T. If the solenoid winding has 2000 turns/m, what is the required current in the solenoid? 2000 A 398 A 4 mA 3979 A 25m A

out of the page

A wire carries a current I as shown below. The magnetic field at the position P points down. up. out of the page. into the page. left. right.

26

A wire carries a steady current of 15.3 A. What total charge (in C) passes through a cross-sectional area of the wire in a 1.7 s time interval? Enter a number with one digit behind the decimal point.

6.33

A wire carries a steady current of 4.6 A. A straight section of the wire is 0.99 m long and lies along the y-axis within a uniform field B = 1.39 T in the z-direction. What is magnitude of the magnetic force on the section of wire in N. Enter a number with two digits behind the decimal point.

increases by 1.6*10^-17 J

An electron travels through free space from point A, which is at 100 V, to point B, which is at 200 V. The kinetic energy of the electron during this trip stays constant. increases by 1.6*10-17 J. decreases by 1.6*10-17 J. decreases by 100 V. increases by 100 V.

II and IV are correct

Charges Q1 and Q2 are situated as shown below. The electric field is zero at point P. What conclusions can be drawn about the charges Q1 and Q2? I. The magnitudes of Q1 and Q2 are equal. II. The magnitude of Q1 is greater than the magnitude of Q2. III. The magnitude of Q1 is less than the magnitude of Q2. IV. Q1 and Q2 have the same sign. V. Q1 and Q2 have different signs. I and IV are correct. II and IV are correct. II and V are correct. III and IV are correct. III and V are correct.

the magnetic force on the wire points towards the left

Consider the situation shown below. A wire carrying a current flowing into the page is placed between the poles of a horseshoe magnet. Which statement is correct regarding the magnetic force on the wire? No magnetic force acts on the wire, since it has no net charge. The magnetic force on the wire points towards the right. The magnetic force on the wire points towards the left. The magnetic force on the wire points towards the top of the page. The magnetic force on the wire points towards the bottom of the page..

15 kΩ

Determine the equivalent resistance between points A and B in the following circuit. 34 kΩ 1.21 kΩ 13.5 kΩ 23.7 kΩ 15 kΩ

D

Equipotential lines are shown. For which region is the magnitude of the electric field the greatest? A B C D it is the same everywhere

the charge at B is positive and the charge at A is negative

Equipotential lines around several point charges are shown. What are the signs of the charges at points A and B? Both charges are positive. Both charges are negative. The charge at A is positive and the charge at B is negative. The charge at B is positive and the charge at A is negative. This cannot be determined fro the information on the diagram.

A: to the right B: up

Equipotential lines around two point charges are shown. What is the direction of the electric field at points A ans B? A: to the right B: to the left The electric field has no direction. A: to the left B: down A: to the right B: up A: to the right B: to the right

66.3

Find the current I (in A) in a long straight wire that would produce a magnetic of 2.9*10-4 T at a distance of 4.57 cm from the wire. Enter a positive number with one digit behind the decimal point.

4.92

Find the magnitude of the electric field produced by a point charge q = 4.93 nanoCoulomb a distance r = 3 meters from the charge in units of N/C. Enter a number with two digits behind the decimal point.

117.74

How much energy (in milliJ) is stored in a 70 microFarad capacitor if the voltage across the capacitor is 58 V? Enter a number with two digits behind the decimal point.

τ = 1 s

In a series RC circuit a charged capacitor with capacitance C is being discharged though a resistor of resistance R. Plots of voltage and current versus time are shown below. Find the time constant τ of the circuit. τ = 4 s τ = 2 s τ = 1 s τ = 0.5 s τ = 0

1

In the early universe and in stars, deuterium nuclei are produced from the combination of one proton and one neutron, with the release of a gamma ray. What is the charge on a deuterium nucleus in units of qe = 1.6*10-19 C? 0 1 -1 2 -2

0

Point P is at a perpendicular distance x from each wire carry current I in the directions indicated. What is the magnetic field B at point P? μ0I/(2πx) into the page μ0I/(2πx) out of the page μ0I/(πx) into the page μ0I/(2πx) out of the page 0

+4 pC

Suppose that a picture of electric field lines is drawn following the convention that 2 field lines emerge from a small sphere with 2 pC of charge. In this picture there is an irregular closed surface, the interior of which is hidden, as shown below. The net amount of charge inside the closed surface must be +8 pC +6 pC +4 pC +2 pC 0 pC -2 pC -4 pC -8 pC

5

The figure below shows different ways to connect a light bulb to a battery with wires. Which of the bulbs will light up? 1 2 3 4 5

4472 V

The immediate cause of many deaths is ventricular fibrillation, an uncoordinated quivering of the heart as opposed to proper beating. An electric current discharged to the chest can cause momentary paralysis of the heart muscle, after which the heart will sometimes start organized beating again. A defibrillator is a device that applies a strong electric shock to the chest over a time interval of a few milliseconds. Assume that an energy of 300 J is to be delivered from the defibrillator, having a 30.0 microFarad capacitance. To what potential difference must the defibrillator be charged? 4472 V 20 V 316 V 200000 V 10000 V

they are oriented randomly

The magnetic domains in a non-magnetized piece of iron are characterized by which orientation? They are all aligned parallel to each other. Adjacent domains are aligned anti-parallel to each other. They are oriented randomly. Adjacent domains are oriented perpendicular to each other. Adjacent domains are aligned at 45o with respect to each other.

7.18

The normal of a one-turn circular loop of radius r = 2.3 cm makes an angle of 48.4 degrees with the direction of a uniform magnetic field of magnitude 1.7 T. What is the magnitude of the torque (in milliNewton m) exerted on the loop by the field when a current I = 3.4 A circulates in the loop? Enter a number with two digits behind the decimal point.

particles 1 and 5

The paths of several particle moving through a region with a magnetic field pointing into the page are shown. Which particles are positively charged? Particles 1 and 5 Particles 2 and 4 Particles 1 2 and 4 Particles 1 and 2 Particles 3 and 5

2087

The potential difference between the two plates of the capacitor shown below is 9.6 V. If the separation between the plates is 4.6 mm, what is the strength of the electric field between the plates N/C? Enter an integer.

1.26 cm

The resistivity of aluminum is 58% higher than that of copper. A copper high voltage line has diameter 1 cm. If is replaced by an aluminum line of the same resistance and length, the aluminum line has diameter 1.58 cm. 1.26 cm. 0.8 cm. 0.64 cm.

IT = I1 = I2 = I3

Three resistors connected in series carry currents labeled I1, I2, I3, respectively. Which of the following expresses the value of the total current IT in the system made up of the three resistors? IT = I1 + I2 + I3 IT = (1/I1 + 1/I2 + 1/I3)-1 IT = (1/I1 + 1/I2 + 1/I3) IT = 3I1 = 3I2 = 3I3 IT = I1 = I2 = I3

electrons have been transferred to the object

Through rubbing an object has acquired a charge of -1 nanoCoulomb. Electrons have been transferred to the object. The object must be made out of conducting material. The object must be made out of insulating material. 6.25*10-9 protons have been rubbed off the object. The object is a semiconductor.

918

Two 0.5 microCoulomb charges are 4.9 m apart. What is the potential at each charge due to the other in V? Enter an integer.

55.1

Two 3.5 microCoulomb charges are 2 m apart. How much energy (in milliJoule) went into assembling these two charges? Enter a number with one digit behind the decimal point.

C

Two balls rest on a frictionless surface. One ball is given a charge of +Q. The other ball is given a charge of +3Q. Which diagram best represents the magnitude and direction of the force vectors on the balls? A B C D None

C1 = 4 pF, C2 = 4 pF

Two capacitors have an equivalent capacitance of 8 pF if connected in parallel, and 2 pF, if connected in series. Find C1 and C2. C1 = 8 pF, C2 = 2 pF C1 = 8 pF, C2 = 1 pF C1 = 3 pF, C2 = 5 pF C1 = 4 pF, C2 = 4 pF This cannot be determined from the information given.

The 50 W bulb has twice the resistance as the 100 W bulb.

Two light bulbs, one rated at 50 W and a second rated at 100 W, are both supposed to be connected to a 110 V source of emf. Which one of the following is true? The 50 W bulb has twice the resistance as the 100 W bulb. The 50 W bulb has half the resistance as the 100 W bulb. The 50 W bulb has four times the resistance as the 100 W bulb. Both bulbs have the same resistance, since they are connected to the same 110 V emf. The 50 W bulb has one quarter the resistance as the 100 W bulb.

37.34

Two positive point charges, each with charge q, separated by a distance d, repel each other with a force of magnitude 10 N. What is the magnitude of the force between two positive point charges of magnitude 6.57 q, separated by a distance 3.4 d in units of N? Enter a number with two digits behind the decimal point.

5

Two uniformly charged spheres are firmly fastened to and electrically insulated from frictionless pucks on an air table. The charge on sphere 2 is three times the charge on sphere 1. Which force diagram correctly shows the magnitude and direction of the electrostatic forces? 1 2 3 4 5 6 7

100 microFarad

What is the capacitance of the series RC circuit referred to in the previous problem? 100 microFarad 0.01 Farad 10 picoFarad 1 Farad 2 microFarad

the negative z-direction

What is the direction of the magnetic force on the wire segment cd? the x-direction the z-direction the negative x-direction the negative z-direction the y-direction none of the above.

10000 Ω

What is the resistance of the series RC circuit referred to in the previous problem? 4 Ω 1 Ω 100 Ω 2000 Ω 10000 Ω

4 s

What is the time constant for the discharge of this capacitor? The capacitor does not discharge because the resistors cancel each other. 1 s 2 s 5 s 4 s

move with constant acceleration

When a positive charge is released from rest in a uniform electric field, it will remain at rest. move with constant acceleration. move with constant velocity. move with linearly increasing acceleration.

1

Which compass shows the correct direction of the magnet field at point A? 1 2 3 4 5

E- the potential is positive very close to a positive charge and negative very close to a negative charge

Which of the charge configurations depicted would give rise to the potential shown below? A B C D E- The potential is positive very close to a positive charge and negative very close to a negative charge.

(a), (d), (e), (h) only

Which of the following are true of static charges on everyday objects? (a) Like charges repel. (b) Like charges attract. (c) Opposite charges repel. (d) Opposite charges attract. (e) A positively charged object has lost electrons. (f) A positively charged object has gained protons. (g) A negatively charged object has lost protons. (h) A negatively charged object has gained electrons. (a) and (d) only (b), (c), (f), (g) only (a), (d), (e), (f), (g), (h) only (a), (d), (e), (h) only (a), (d), (f), (g) only (c) and (h) only

(b), (d), (e), (f) only

Which of the following are true of static charges on everyday objects? (a) Like charges repel. (b) Like charges attract. (c) Opposite charges repel. (d) Opposite charges attract. (e) A positively charged object has lost electrons. (f) A positively charged object has gained protons. (g) A negatively charged object has lost protons. (h) A negatively charged object has gained electrons. (a) and (d) only (b), (c), (f), (g) only (a), (d), (e), (f), (g), (h) only (a), (d), (e), (h) only (a), (d), (f), (g) only (c) and (h) only

all the above statements are true

Which of the following statements about a conductor in electrostatic equilibrium is false? The electric field inside the conductor is zero. Just outside the conductor, the electrostatic field is perpendicular to its surface. The net charge inside the conductor is zero, all excess charge resides on the surface. A charge located within a hole in a conductor at equilibrium feels no force from charges outside the conductor. All the above statements are true.

(a) and (f) only

Which of the following statements are true about the electric potential or the electric potential difference? (a) The SI unit of the electric potential is volts (V). (b) The electric potential can also be expressed in units of Joules. (c) The electric potential produced by a charge at a given location provides a measure of the rate at which charge flows past that point. (d) As a positive charge moves in the direction of an electric field, it gains electric potential. (f) The electric potential difference between two points is the difference in potential energy possessed by another charge at those two points, divided by this charge. (a) only (a) and (b) only (a), (d), and (f) only (a) and (f) only All statements are true.

1 and 4

Which of the points shown in the figure below are at the same potential? 2 and 5. 2, 3, and 5. 1 and 4. 1 and 5. 2 and 4.