Question 1

A circuit consists of a resistor $$R$$ and a capacitor $$C in $$series with a battery. At the moment the switch is closed, what is the initial current through the resistor?

Accepted Answer

$$I_0$$ = \dfrac{V}{R}$$

Question 2

In an RC circuit, the voltage across the capacitor as a function of time is given by $$V_C(t) = V_0$ (1 - e$$^{-t/RC}$$). $$What is the time constant $$	au of $$the circuit?

Accepted Answer

$$	au = RC$$

Question 3

A charged particle moves in a region with a constant magnetic field directed out of the page. If the particle's velocity is perpendicular to the field, what is the shape of its trajectory?

Accepted Answer

A circle

Question 4

A thick copper cylinder has an outer radius $$2R$$ and inner radius $$R$$ and carries a current $$I. $$Which statement is TRUE about the magnetic field in the hollow region ($$R \u003c r \u003c 2R) of $$the cylinder?

Accepted Answer

The magnetic field is zero in this region.

Question 5

A conducting loop is moving with constant velocity $$v$$ entering a region with a uniform magnetic field $$B$$ directed into the page. What is the direction of the induced current in the loop?

Accepted Answer

Clockwise

Question 6

A long solenoid has inductance $$L$$, and a current $$I is $$flowing through it. Which of these increases the inductance of the solenoid?

Accepted Answer

Increase the number of turns keeping the length constant.

Question 7

A coil with $$N$$ turns, area $$A$$, and current $$I is $$placed in a uniform magnetic field $$B$$ pointing in the $$+z$$ direction. What is the magnitude of the magnetic dipole moment of the coil?

Accepted Answer

$$\mu = NIA$$

Question 8

A metal rod of length $$L$$ moves with velocity $$v$$ perpendicular to a uniform magnetic field $$B. $$What is the magnitude of the emf generated across the ends of the rod?

Accepted Answer

$$\mathcal{E} = BvL$$

Question 9

A charged particle of mass $$m$$ and charge $$q$$ moves at speed $$v$$ perpendicular to a uniform magnetic field $$B. $$What is the radius $$r of $$its circular path?

Accepted Answer

$$r = \dfrac{mv}{qB}$$

Question 10

A rectangular loop of wire with area $$A$$ and $$N$$ turns is placed in a uniform magnetic field $$B. $$The field is perpendicular to the plane of the loop. What is the maximum torque $$	au_{max}$$ experienced by the loop?

Accepted Answer

$$	au_{max} = NIBA$$

Question 11

A solenoid of length $$l$$, cross-sectional area $$A$$, and $$N$$ turns carries a current $$I. $$What is the magnetic field inside the solenoid?

Accepted Answer

$$B = \mu_0$ \dfrac{N}{l} I$$

Question 12

A circular loop of radius $$R$$ carries a current $$I. $$What is the magnetic field at the center of the loop?

Accepted Answer

$$B = \dfrac{\mu_0$ I}{2R}$$

Question 13

A straight wire carries a current $$I. $$What is the direction of the magnetic field produced by the wire at a point to its right?

Accepted Answer

Out of the page

Question 14

A metal rod moves to the right in a uniform magnetic field directed into the page. What is the direction of the induced current in the rod?

Accepted Answer

Upward along the rod

Question 15

A rectangular loop is pulled with constant velocity $$v$$ into a region of uniform magnetic field $$B$$ perpendicular to the loop. What is the induced emf in the loop while it is entering the field?

Accepted Answer

$$\mathcal{E} = B l v$$

Question 16

A charged particle moves in a uniform magnetic field. If its velocity is parallel to the field, what is the magnetic force on the particle?

Accepted Answer

Zero

Question 17

A solenoid is connected to a battery and a switch. When the switch is opened, what happens to the current in the solenoid?

Accepted Answer

It decreases rapidly to zero

Question 18

A coil with $$N$$ turns and area $$A is $$placed in a time-varying magnetic field $$B(t). $$What is the induced emf in the coil?

Accepted Answer

$$\mathcal{E} = -N A \dfrac{dB}{dt}$$

Question 19

A rectangular loop of wire is placed in a uniform magnetic field. The field is perpendicular to the plane of the loop. If the area of the loop is doubled, what happens to the maximum torque on the loop?

Accepted Answer

It doubles

Magnetic Fields, Forces, and Induction: Study Notes for College Physics

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