Question 1

A square loop of wire with side length $$a is $$placed in a uniform magnetic field $$B$$ perpendicular to the plane of the loop. If the magnetic field is increased from $$B_0 to$$ $$B_1 in $$time $$t$$, what is the magnitude of the average induced emf in the loop?

Accepted Answer

$$\frac{a^2$ (B_1$ - B_0$)}{t}$$

Question 2

An LC circuit consists of a capacitor $$C$$ and an inductor $$L. If $$the initial charge on the capacitor is $$Q_0$$, what is the maximum current in the circuit?

Accepted Answer

$$\frac{Q_0$}{\sqrt{LC}}$$

Question 3

A long straight wire carries a current $$I$$ upward. A second parallel wire, a distance $$d$$ away, carries the same current downward. What is the direction of the magnetic field at a point exactly midway between the wires?

Accepted Answer

Into the page

Question 4

A copper ring lies flat on a table as shown. A bar magnet is dropped through the ring with its north pole facing downward. As the magnet falls, what is the direction of the induced current in the ring (viewed from above)?

Accepted Answer

Counterclockwise

Question 5

Which of the following statements about the energy stored in an inductor is correct?

Accepted Answer

It is given by $$\frac{1}{2} L I^2$

Question 6

A solenoid of length $$l$$ and $$N$$ turns carries a current $$I. $$What is the magnitude of the magnetic field inside the solenoid (far from the ends)?

Accepted Answer

$$\mu_0$ \frac{N}{l} I$$

Question 7

A wire loop is rotated in a uniform magnetic field. Which of the following will NOT increase the maximum induced emf?

Accepted Answer

Increasing the resistance of the loop

Question 8

A charged particle moves with velocity $$\vec{v}$$ perpendicular to a uniform magnetic field $$\vec{B}. $$What is the radius of the circular path it follows?

Accepted Answer

$$\frac{mv}{qB}$$

Question 9

A resistor $$R$$ and an inductor $$L$$ are connected in series to a battery of emf $$\mathcal{E}. $$Immediately after the switch is closed, what is the current through the resistor?

Accepted Answer

$$0$$

Question 10

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

Accepted Answer

$$\frac{\mu_0$ I}{2r}$$

Question 11

A straight wire carries a current $$I in $$the positive $$x-$$direction. At a point located a distance $$d$$ above the wire (in the $$y-$$direction), what is the direction of the magnetic field?

Accepted Answer

Into the page

Question 12

A conducting rod of length $$l$$ moves with velocity $$v$$ perpendicular to a uniform magnetic field $$B. $$What is the emf induced between the ends of the rod?

Accepted Answer

$$Blv$$

Question 13

A toroid has $$N$$ turns, carries current $$I$$, and has a mean radius $$r. $$What is the magnetic field inside the toroid?

Accepted Answer

$$\frac{\mu_0$ N I}{2\pi r}$$

Question 14

A wire loop of area $$A is $$oriented perpendicular to a uniform magnetic field $$B. If $$the field decreases at a constant rate $$\frac{dB}{dt}$$, what is the induced emf in the loop?

Accepted Answer

$$-A \frac{dB}{dt}$$

Question 15

A proton moves in a region where there is a uniform electric field $$\vec{E}$$ and a uniform magnetic field $$\vec{B}$$, both directed along the $$x-$$axis. If the proton moves with velocity $$\vec{v} in $$the $$y-$$direction, what is the direction of the net force on the proton?

Accepted Answer

In the $$z-$$direction

Question 16

A transformer has 100 turns on the primary coil and 500 turns on the secondary coil. If the input voltage is $$120\ \mathrm{V}$$, what is the output voltage (assuming 100% efficiency)?

Accepted Answer

$$600\ \mathrm{V}$$

Question 17

A rectangular loop of wire is pulled at constant speed $$v$$ out of a region of uniform magnetic field $$B. $$What is the direction of the induced current in the loop as it leaves the field?

Accepted Answer

Such that it creates a magnetic field into the page

Electromagnetic Induction, Magnetic Fields, and Circuits: Study Notes for Physics 10320 Exam 3

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