Question 1

Which of the following statements best explains why the north end of a compass needle points toward the geographic North Pole of the Earth?

Accepted Answer

The geographic North Pole is a magnetic south pole.

Question 2

A long straight wire carries a current $$I. At a $$distance $$r$$ from the wire, what is the magnitude of the magnetic field produced by the wire?

Accepted Answer

$$B = \frac{\mu_0$ I}{2\pi r}$$

Question 3

If two long, parallel wires carry currents in the same direction, what is the nature of the force between them?

Accepted Answer

They attract each other.

Question 4

A charged particle with charge $$q$$ moves with velocity $$\vec{v}$$ perpendicular to a uniform magnetic field $$\vec{B}. $$What is the magnitude of the force acting on the particle?

Accepted Answer

$$F = qvB$$

Question 5

A solenoid has $$N$$ turns, length $$\ell$$, and carries a current $$I. $$What is the magnitude of the magnetic field inside the solenoid?

Accepted Answer

$$B = \frac{\mu_0$ N I}{\ell}$$

Question 6

Which of the following best describes the behavior of magnetic field lines?

Accepted Answer

They form closed loops.

Question 7

A mass spectrometer uses perpendicular electric and magnetic fields to select particles of a specific velocity. What is the velocity $$v of a $$particle that passes through undeflected?

Accepted Answer

$$v = \frac{E}{B}$$

Question 8

Which of the following is true about ferromagnetic materials?

Accepted Answer

They are made up of domains that can be aligned by an external magnetic field.

Question 9

A current-carrying wire of length $$\ell is $$placed in a uniform magnetic field $$B$$ perpendicular to the wire. What is the magnitude of the force on the wire?

Accepted Answer

$$F = I \ell B$$

Question 10

Which device uses the torque on a current loop in a magnetic field to measure electric current?

Accepted Answer

Galvanometer

Question 11

A rectangular current loop of area $$A$$ and $$N$$ turns carries a current $$I in a $$uniform magnetic field $$B. $$What is the maximum torque on the loop?

Accepted Answer

$$	au = N I A B$$

Question 12

Which of the following best describes the effect of inserting an iron core into a solenoid?

Accepted Answer

The magnetic field inside the solenoid increases.

Question 13

What is the SI unit of the magnetic field $$B$$?

Accepted Answer

Tesla (T)

Question 14

Which of the following is a correct application of Ampère’s Law?

Accepted Answer

Calculating the magnetic field inside a long solenoid.

Question 15

A loudspeaker converts electrical signals into sound using which physical principle?

Accepted Answer

A magnet exerts a force on a current-carrying wire.

Question 16

If a bar magnet is cut in half, what happens to its magnetic poles?

Accepted Answer

Each piece becomes a magnet with both a north and a south pole.

Question 17

Which of the following best describes magnetic hysteresis in ferromagnetic materials?

Accepted Answer

The lag between the applied magnetic field and the resulting magnetization.

Question 18

A proton moves in a circle of radius $$r in a $$uniform magnetic field $$B. If $$the speed of the proton is doubled, what happens to the radius of its path?

Accepted Answer

It doubles.

Question 19

Which of the following is NOT a property of magnetic field lines?

Accepted Answer

They cross each other.

Question 20

The force per unit length between two parallel wires carrying currents $$I_1$$ and $$I_2$$ separated by distance $$d is $$given by which equation?

Accepted Answer

$$\frac{F}{\ell} = \frac{\mu_0$ I_1$ I_2$}{2\pi d}$$

Chapter 20: Magnetism – Physics Study Notes

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