Exam

Name___________________________________

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

1) The figure shows a steady electric current passing through a wire with a narrow region.What happens to the drift velocity of the moving charges as they go from region A toregion B and then to region C?

A) The drift velocity increases from A to B and decreases from B to C.B) The drift velocity remains constant.C) The drift velocity decreases from A to B and increases from B to C.D) The drift velocity increases all the time.E) The drift velocity decreases all the time.

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2) When electric current is flowing in a metal, the electrons are movingA) at the speed of sound in the metal.B) at none of the above speeds.C) at the speed of light.D) at nearly the speed of light.E) at the speed of sound in air.

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3) A narrow copper wire of length L and radius b is attached to a wide copper wire oflength L and radius 2b, forming one long wire of length 2L. This long wire is attachedto a battery, and a current is flowing through it. If the electric field in the narrow wire isE, the electric field in the wide wire isA) E/4. B) E. C) 2E. D) 4E. E) E/2.

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4) The figure shows a 2.0-cm diameter roller that turns at 90 rpm. A 4.0-cm wide plasticfilm is being wrapped onto the roller, and this plastic carries an excess electric chargehaving a uniform surface charge density of 5.0 nC/cm2. What is the current of themoving film?

A) 30 nA B) 11 µA C) 190 nA D) 23 µA

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5) The emf and the internal resistance of a battery are as shown in the figure. If a currentof 8.3 A is drawn from the battery when a resistor R is connected across the terminalsab of the battery, what is the power dissipated by the resistor R?

A) 790 W B) 440 W C) 700 W D) 530 W E) 620 W

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6) As more resistors are added in parallel across a constant voltage source, the powersupplied by the sourceA) decreases. B) increases. C) does not change.

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7) The figure shows three identical lightbulbs connected to a battery having a constantvoltage across its terminals. What happens to the brightness of lightbulb 1 when theswitch S is closed?

A) The brightness remains the same as before the switch is closed.B) The brightness decreases permanently.C) The brightness will increase momentarily then return to its previous level.D) The brightness increases permanently.E) The brightness will decrease momentarily then return to its previous level.

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8) A resistor is made out of a long wire having a length L. Each end of the wire is attachedto a terminal of a battery providing a constant voltage V0. A current I flows through thewire. If the wire were cut in half, making two wires of length L/2, and both wires wereattached to the battery (the end of both wires attached to one terminal, and the otherends attached to the other terminal), what would be the total current flowing throughthe two wires?A) 4I B) 2I C) I/2 D) I/4 E) I

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9) An RC circuit is connected across an ideal DC voltage source through an open switch.The switch is closed at time t = 0 s. Which of the following statements regarding thecircuit are correct?A) The potential difference across the resistor is always greater than the potential

difference across the capacitor.B) Once the capacitor is essentially fully charged, there is no appreciable current in

the circuit.C) The potential difference across the resistor and the potential difference across the

capacitor are always equal.D) The potential difference across the capacitor is always greater than the potential

difference across the resistorE) The capacitor charges to its maximum value in one time constant and the current

is zero at that time.

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10) A light bulb is connected in the circuit shown in the figure with the switch S open andthe capacitor uncharged. The battery has no appreciable internal resistance. Which oneof the following graphs best describes the brightness B of the bulb as a function of timet after closing the switch?

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A) 1 B) 2 C) 3 D) 4 E) 5

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11) In the circuit shown in the figure, an ideal ohmmeter is connected across ab with theswitch S open. All the connecting leads have negligible resistance. The reading of theohmmeter will be closest to

A) 40 Ω. B) 60 Ω. C) 10 Ω. D) 30 Ω. E) 7.5 Ω.

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12) Two identical resistors of resistance R = 24 Ω and a variable resistor Rx are connectedto an ideal battery of voltage V as shown in the figure. What should be the value of the

variable resistance Rx to make the voltage across the two parallel resistors equal to V5

?

A) 40 Ω B) 8.0 Ω C) 4.0 Ω D) 16 Ω E) 24 Ω

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13) A multiloop circuit is shown in the figure. It is not necessary to solve the entire circuit.The current I2 is closest to

A) zero. B) 8 A. C) -8 A. D) -6 A. E) 6 A.

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14) Three particles travel through a region of space where the magnetic field is out of thepage, as shown in the figure. The electric charge of each of the three particles is,respectively,

A) 1 is neutral, 2 is positive, and 3 is negative.B) 1 is neutral, 2 is negative, and 3 is positive.C) 1 is negative, 2 is neutral, and 3 is positive.D) 1 is positive, 2 is neutral, and 3 is negative.E) 1 is positive, 2 is negative, and 3 is neutral.

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15) A charged particle is moving with speed v perpendicular to a uniform magnetic field. Asecond identical charged particle is moving with speed 2v perpendicular to the samemagnetic field. If the frequency of revolution of the first particle is f, the frequency ofrevolution of the second particle isA) 2f. B) f. C) 4f. D) f/2. E) f/4.

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16) A uniform magnetic field of magnitude 0.80 T in the negative z-direction is present in aregion of space, as shown in the figure. A uniform electric field is also present. Anelectron that is projected with an initial velocity v0 = 9.1 × 104 m/s in the positivex-direction passes through the region without deflection. What is the electric fieldvector in the region?

A) -73 kV/m jB) +110 kV/m jC) +110 kV/m iD) +73 kV/m iE) -110 kV/m j

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17) A proton starting from rest travels through a potential of 1.0 kV and then moves into auniform 0.040-T magnetic field. What is the radius of the proton's resulting orbit?(mproton = 1.67 × 10-27 kg, e = 1.60 × 10-19 C)A) 0.17 m B) 0.11 m C) 0.14 m D) 0.080

mE) 0.19 m

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18) An L-shaped metal machine part is made of two equal-length segments that areperpendicular to each other and carry a 4.50-A current as shown in the figure. This parthas a total mass of 3.80 kg and a total length of 3.00 m, and it is in an external 1.20-Tmagnetic field that is oriented perpendicular to the plane of the part, as shown. What isthe magnitude of the NET magnetic force that the field exerts on the part?

A) 11.5 N B) 32.4 N C) 8.10 N D) 16.2 N E) 22.9 N

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19) A rectangular loop of wire carrying a 4.0-A current is placed in a magnetic field of 0.60T. The magnitude of the torque acting on this wire when the plane of the loop makes a30° angle with the field is measured to be 1.1 N • m. What is the area of this loop?A) 0.26

m2B) 0.53

m2C) 0.20

m2D) 0.40

m2E) 0.80

m2

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20) A round loop of diameter 12 cm, carrying a current of 0.40 A, is placed inside a

magnetic field B = 0.20 T i + 0.40 T j . The normal to the loop is parallel to the unitvector n = -0.60 i - 0.80 j. What is the potential energy of the loop?A) +4.5 × 10-3 JB) -4.5 × 10-3 JC) -2.3 × 10-3 JD) +2.0 × 10-3 JE) -2.0 × 10-3 J

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Answer KeyTestname: F17MT2

1) A2) B3) A4) C5) B6) B7) D8) A9) B10) B11) E12) B13) D14) C15) B16) A17) B18) A19) B20) D

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