Phys Final

An electron (charge = -1.6 × 10-19 C) is moving at 3.0 × 105 m/s in the positive x direction. A magnetic field of 0.80 T is in the positive z direction. The magnetic force on the electron is

4.5 × 10-14 N in the positive y direction

The flux of the electric field (24 N/C) + (30 N/C) + (16 N/C) through a 2.0 m2 portion of the yz plane is

48 N m2/C

An ideal battery has an emf of 12 V. If it is connected to a circuit and creates a current of 4.0 A, what is the power

48 W

A point source emits electromagnetic energy at a rate of 100 W. The intensity 10 m from the source is

0.080 W/m2

Charge is distributed uniformly along a long straight wire. The electric field 2 cm from the wire is 20 N/C. The electric field 4 cm from the wire is

10 N/C

Radio waves of wavelength 3 cm have a frequency of:

10,000 MHz

A ball is held 50 cm in front of a plane mirror. The distance between the ball and its image is

100 cm

An electric dipole consists of two charges, ±2.5 μC, separated by 1.0 x 10-4 m and centered on the origin. If the dipole is oriented along the x axis, what is the electric field at x = 15 cm

1300 N/C

A certain capacitor, in series with a resistor, is being charged. At the end of 10 ms its charge is half the final value. The time constant for the process is about

14 ms

A flat coil of wire, having 5 turns, has an inductance L. The inductance of a similar coil having 20 turns is

16L

A battery of emf 24 V is connected to a 6-Ω resistor. As a result, current of 3 A exists in the resistor. The terminal potential difference of the battery is

18 V

A 60-watt light bulb carries a current of 0.5 ampere. The total charge passing through it in one hour is

1800 C

The magnetic field a distance 2 cm from a long straight current-carrying wire is 2 × 10-5 T. The current in the wire is

2.0 A

Positive charge Q is placed on a conducting spherical shell with inner radius R1 and outer radius R2. A point charge q is placed at the center of the cavity. The magnitude of the electric field at a point outside the shell, a distance r from the center, is

(q + Q)/4πε0r2

A converging lens of focal length 20 cm is placed in contact with a diverging lens of focal length 30 cm. The focal length of this combination is

+60 cm

A particle with a charge of 5.5 × 10-8C charge is fixed at the origin. A particle with a charge of-2.3 × 10-8C charge is moved from x = 3.5 cm on the x axis to y = 3.5 cm on the y axis. The change in the potential energy of the two-charge system is

0 J

A loop of current-carrying wire has a magnetic dipole moment of 5.0 × 10-4 Am2. If the dipole moment makes an angle of 57° with a magnetic field of 0.35 T, what is its potential energy?

-9.5 x 10-5 J

A charged capacitor stores 10 C at 40 V. Its stored energy is

200 J

Capacitor C1 is connected alone to a battery and charged until the magnitude of the charge on each plate is 4.0 × 10-8 C. Then it is removed from the battery and connected to two other capacitors C2 and C3, as shown. The charge on the positive plate of C1 is then 1.0 × 10-8 C. The charges on the positive plates of C2 and C3 are

q2 = 3.0 × 10--8 C and q3 = 3.0 × 10-8 C

A battery has an emf of 9 V and an internal resistance of 2 Ω. If the potential difference across its terminals is greater than 9 V

the current must be out of the negative terminal

Positive charge Q is distributed uniformly throughout an insulating sphere of radius R, centered at the origin. A particle with a positive charge Q is placed at x = 2R on the x axis. The magnitude of the electric field at x = R/2 on the x axis is

Q/72πε0R2

A 2-μF and a 1-μF capacitor are connected in series and charged from a battery. They store charges P and Q, respectively. When disconnected and charged separately using the same battery, they have charges R and S, respectively. Then

R > S > Q = P

A certain ammeter has an internal resistance of 1 Ω and a range from 0 to 50 mA. To make its range from 0 to 5 A, use

a resistance of 1/99 Ω in parallel

A particle with a charge of 5 × 10-6 C and a mass of 20 g moves uniformly with a speed of 7 m/s in a circular orbit around a stationary particle with a charge of -5 × 10-6 C. The radius of the orbit is

0.23 m

A 300-N/C uniform electric field points perpendicularly toward the left face of a large neutral conducting sheet. The area charge density on the left and right faces, respectively, are

-2.7 × 10-9 C/m2; +2.7 × 10-9 C/m 2

A particle with a charge of 5.5 × 10-6 C is 3.5 cm from a particle with a charge of -2.3 ×10-8 C. The potential energy of this two-particle system, relative to the potential energy at infinite separation, is:

-3.3 × 10-2 J

If the electric field is in the positive x direction and has a magnitude given by E = Cx2, where C is a constant, then the electric potential is given by V =

-Cx3/3

A circular loop of wire with a radius of 20 cm lies in the xy plane and carries a current of 2 A, counterclockwise when viewed from a point on the positive z axis. Its magnetic dipole moment is

0.25 Am2, in the positive z direction

Each of the three 25-μF capacitors shown is initially uncharged. How many coulombs of charge pass through the ammeter A after the switch S is closed?

0.30 C

A loop of wire carrying a current of 2.0 A is in the shape of a right triangle with two equal sides, each 15 cm long. A 0.7 T uniform magnetic field is in the plane of the triangle and is perpendicular to the hypotenuse. The resultant magnetic force on the two equal sides has a magnitude of

0.30 N

A 20-μF capacitor is charged to 200 V. Its stored energy is

0.4 J

A current of 1 A is used to charge a parallel plate capacitor with square plates. If the area of each plate is 0.6 m2 the displacement current through a 0.3 m2 area wholly between the capacitor plates and parallel to them is:

0.5 A

Each of the four capacitors shown is 500 μF. The voltmeter reads 1000V. The magnitude of the charge on each capacitor plate is

0.5 C

A 3-Ω and a 1.5-Ω resistor are wired in parallel and the combination is wired in series to a 4-Ω resistor and a 10-V emf device. The current in the 3-Ω resistor is:

0.67 A

A battery with an emf of 12 V and an internal resistance of 1 Ω is used to charge a battery with an emf of 10 V and an internal resistance of 1 Ω. The current in the circuit is

1 A

Radio waves of wavelength 300 m have a frequency of

1 MHz

A 1-μF capacitor is connected to an emf that is increasing uniformly with time at a rate of 100 V/s. The displacement current between the plates is

1 × 10-4 A

A 0.70-m radius cylindrical region contains a uniform electric field that is parallel to the axis and is increasing at the rate 5.0 × 1012 V/m⋅s. The magnetic field at a point 1.2 m from the axis has a magnitude of

1.1 × 10-5 T

A particle with charge 2μC is placed at the origin. An identical particle, with the same charge, is placed 2 m from the origin on the x axis, and a third identical particle, with the same charge, is placed 2 m from the origin on the y axis. The magnitude of the force on the particle at the origin is

1.3 × 10-2 N

In an antique automobile, a 6-V battery supplies a total of 48 W to two identical headlights in parallel. The resistance of each bulb is

1.5 Ω

A strip 1.2 mm wide is moving at a speed of 25 cm/s through a uniform magnetic field of 5.6 T. What is the maximum Hall voltage across the strip

1.7 mV

Two long straight wires pierce the plane of the paper at vertices of an equilateral triangle as shown below. They each carry 2.0 A, out of the paper. The magnetic field at the third vertex (P) has magnitude

1.7 × 10-5 T

An electric dipole consists of a particle with a charge of +6 × 10-6 C at the origin and a particle with a charge of -6 × 10-6 C on the x axis at x = 3 × 10-3 m. Its dipole moment is

1.8 × 10-8 Cm, in the negative x direction

A convex refracting surface has a radius of 12 cm. Light is incident in air (n = 1) and refracted into a medium with an index of refraction of 2. To obtain light with rays parallel to the central axis after refraction a point source should be placed on the axis

12 cm from the surface

Two large insulating parallel plates carry positive charge of equal magnitude that is distributed uniformly over their inner surfaces. Rank the points 1 through 5 according to the magnitude of the electric field at the points, least to greatest.

2 and 3 tie, then 1 and 4 and 5 tie

Resistances of 2.0 Ω, 4.0 Ω, and 6.0 Ω and a 24-V battery are all in series. The current in the 2.0 Ω resistor is

2.0 A

A 3-Ω and a 1.5-Ω resistor are wired in parallel and the combination is wired in series to a 4-Ω resistor and a 10-V emf device. The potential difference across the 3-Ω resistor is

2.0 V

A uniform electric field of 300 N/C makes an angle of 25° with the dipole moment of an electric dipole. If the torque exerted by the field has a magnitude of 2.5 × 10-7 Nm, the dipole moment must be:

2.0 × 10-9 Cm

A 5.0-ft woman wishes to see a full length image of herself in a plane mirror. The minimum length mirror required is

2.5 ft

Two long straight wires enter a room through a window. One carries a current of 3.0 A into the room while the other carries a current of 5.0 A out. The magnitude of the path integral around the window frame is

2.5 × 10-6 T⋅m

A wire contains a steady current of 2 A. The number of electrons that pass a cross section in 2 s is

2.5 × 1019

Two long straight wires are parallel and carry current in opposite directions. The currents are 8.0 A and 12 A and the wires are separated by 0.40 cm. The magnetic field at a point midway between the wires is

20 × 10-4 T

A certain capacitor, in series with a 720-Ω resistor, is being charged. At the end of 10 ms its charge is half the final value. The capacitance is about

20 μF

A 45-m long wire is coiled so that it makes a coil containing 100 circular loops, one on top of the other. If the wire carries a current of 13 A, what is the magnetic dipole moment of the coil?

21 Am2

A student kept her 60-watt, 120-volt study lamp turned on from 2:00 PM until 2:00 AM. How much charge went through it

21,600 C

A current of 0.3 A passes through a lamp for 2 minutes using a 6 V power supply. The energy dissipated by this lamp during the 2 minutes is

216 J

When a piece of paper is held with one face perpendicular to a uniform electric field the flux through it is 25 Nm2/C. When the paper is turned 25° with respect to the field the flux through it is

23 Nm2/C

An incandescent light bulb is marked "60 watt, 120 volt". Its resistance is

240 Ω

A 120-V power line is protected by a 15-A fuse. What is the maximum number of 120 V, 500 W light bulbs that can be operated at full brightness from this line

3

A disk with a uniform positive surface charge density lies in the x-y plane, centered on the origin. The disk contains 2.5 x 10-6 C/m2 of charge, and is 7.5 cm in radius. What is the electric field at z = 15 cm

3.0 x 104 N/C

A 200-N/C electric field is in the positive x direction. The force on an electron in this field is

3.2 × 10-17 N, in the negative x direction

A semi-infinite wire runs along the positive y axis, beginning at the origin (x = y = 0) and extending infinitely far in the +y direction. If the current in the wire is 12 A, what magnetic field does it create on the x axis at the point x = 3.5 cm

3.4 x 10-5 T

The mechanical equivalent of heat is 1 cal = 4.18 J. A heating coil, connected to a 120-V source, develops 60,000 calories in 10 minutes. The current in the coil is

3.5 A

A parallel-plate capacitor has a plate area of 0.2 m2 and a plate separation of 0.1 mm. To obtain an electric field of 2.0 × 106 V/m between the plates, the magnitude of the charge on each plate should be

3.5 × 10-6 C

A coil of 1000 turns of wire has a radius of 12 cm and carries a counterclockwise current of 15A. If it is lying flat on the ground, and the Earth's magnetic field points due north, has a magnitude of 5.8 x 10-5 T, and makes a downward angle of 25° with the vertical, what is the torque on the loop?

3.6 x 10-2 N·m south

At one instant an electron (charge = -1.6 × 10-19 C) is moving in the xy plane, the components of its velocity being vx = 5.0 × 105 m/s and vy = 3.0 × 105 m/s. A magnetic field of 0.80 T is in the positive x direction. At that instant the magnitude of the magnetic force on the electron is

3.8 × 10-14 N

A 0.20-cm radius cylinder, 3.0 cm long, is wrapped with wire to form an inductor. At the instant the magnetic field in the interior is 5.0 mT, the energy stored in the field is

3.8 × 10-6 J

A current of 10 A in a certain inductor results in a stored energy of 40 J. When the current is changed to 5 A in the opposite direction, the stored energy changes by

30 J

A current of 0.5 ampere exists in a 60-ohm lamp. The applied potential difference is

30 V

An electric dipole consists of two equal and opposite charged particles of mass 1.2 g and charge 3.7 μC separated by 1.7 mm. What is the escape speed of the positive charge - that is, how much speed would you have to give it so it would escape the other charge?

350 m/s

A concave spherical mirror has a focal length of 12 cm. If an object is placed 18 cm in front of it the image position is

36 cm in front of the mirror

A wire contains a steady current of 2 A. The charge that passes a cross section in 2 s is

4 C

By using only two resistors, R1 and R2 a student is able to obtain resistances of 3 Ω, 4 Ω, 12 Ω, and 16 Ω. The values of R1 and R2 are

4 Ω, 12 Ω

Four 20-Ω resistors are connected in parallel and the combination is connected to a 20-V emf device. The current in the device is

4.0 A

A total resistance of 3.0 Ω is to be produced by combining an unknown resistor R with a 12 Ω resistor. What is the value of R and how is it to be connected to the 12 Ω resistor

4.0 Ω, parallel

Particle 1 with charge q1, and particle 2, with a charge q2, are on the x axis, with particle 1 at x = a with and particle 2 at x = -2a. For the net force on a third charged particle, at the origin to be zero q1 and q2 must be related by q2=

4q1

A 1-A current is used to charge a parallel plate capacitor. A large square piece of paper is placed between the plates and parallel to them so it sticks out on all sides. The value of the integral around the perimeter of the paper is

4π × 10-7 T⋅m

An iron is marked "120 volt, 600 watt". In normal use, the current in it is

5 A

A 10-ohm resistor has a constant current. If 1200 C of charge flow through it in 4 minutes what is the value of the current

5.0 A

A cylinder has a radius of 2.1 cm and a length of 8.8 cm. Total charge 6.1 × 10-7 C is distributed uniformly throughout. The volume charge density is:

5.0 × 10-3 C/m3

A 10 turn conducting loop with a radius of 3.0 cm spins at 60 revolutions per second in a magnetic field of 0.50 T. The maximum emf generated is

5.3 V

In the figure, if the current element has a length of 1.0 mm, carries a current of 2.5 A, and is a distance of 4.8 cm from the point P, what is the magnitude of the magnetic field at point P?

5.4 x 10-8 T

A 1.2-m radius cylindrical region contains a uniform electric field along the cylinder axis. It is increasing uniformly with time. To obtain a total displacement current of 2.0 × 10-9 A through a cross section of the region, the magnitude of the electric field should change at a rate o

50 V/ms

A 10-turn ideal solenoid has an inductance of 4.0 mH. To generate an emf of 2.0 V the current should change at a rate of

500 A/s

A particle with a charge of 5.5 × 10-8C is fixed at the origin. A particle with a charge of -2.3 × 10-8C is moved from x = 3.5 cm on the x axis to y = 4.3 cm on the y axis. The change in potential energy of the two-particle system is

6.0 × 10-5 J

The Hall effect can be used to calculate the charge-carrier number density in a conductor. If a conductor carrying a current of 2.0 A is 0.5 mm thick, and the Hall effect voltage is 4.5 μV when it is in a uniform magnetic field of 1.2 T, what is the density of charge carriers in the conductor

6.7 x 1027/m3

The magnitude of the force of a 400-N/C electric field on a 0.02-C point charge is

8 N

A charged capacitor is being discharged through a resistor. At the end of one time constant the charge has been reduced by (1 - 1/e) = 63% of its initial value. At the end of two time constants the charge has been reduced by what percent of its initial value

86%

A 5.0-C charge is 10 m from a -2.0-C charge. The electrostatic force is on the positive charge is

9.0 × 108 N toward the negative charge

The electric potential at a certain point is given by V = -7.5x2 + 3x, where V is in volts and x is in meters. What is the electric field at that point?

= (15x - 3)

The critical angle for total internal reflection at a diamond-air interface is 25°. Suppose light is incident at an angle of θ with the normal. Total internal reflection will occur if the incident medium is

diamond and θ > 25°

Resistances of 2.0 Ω, 4.0 Ω, and 6.0 Ω and a 24-V emf device are all in series. The circuit is initially ungrounded. After grounding, the current in the circuit

does not change

A 2-μF and a 1-μF capacitor are connected in series and a potential difference is applied across the combination. The 2-μF capacitor has

half the potential difference of the 1-μF capacitor

A 2-μF and a 1-μF capacitor are connected in parallel and a potential difference is applied across the combination. The 2-μF capacitor has

twice the charge of the 1-μF capacitor

Positive charge +Q is uniformly distributed on the upper half of a rod and a negative charge -Q is uniformly distributed on the lower half. What is the direction of the electric field at point P, on the perpendicular bisector of the rod

↓

An electromagnetic wave is traveling in the positive x direction with its electric field along the z axis and its magnetic field along the y axis. The fields are related by

∂B/∂x = -μ0ε0∂E/∂t