Q: A straight conductor of length $0.5\ \mathrm{m}$ carries a current of $4\ \mathrm{A}$ and is placed at an angle of $30^\circ$ to a uniform magnetic field of flux density $0.2\ \mathrm{T}$. What is the magnitude of the force on the conductor?

$F = BIL\sin\theta = 0.2 \times 4 \times 0.5 \times \sin 30^\circ = 0.2\ \mathrm{N}$

Q: A coil of 100 turns encloses an area of $0.02\ \mathrm{m}^2$ and is placed in a uniform magnetic field of $0.5\ \mathrm{T}$. What is the total magnetic flux linkage?

$\lambda = N\Phi = 100 \times 0.5 \times 0.02 = 1\ \mathrm{Wb}$

Q: A wire of length $0.3\ \mathrm{m}$ carries a current of $2\ \mathrm{A}$ and is placed perpendicular to a magnetic field of $0.4\ \mathrm{T}$. What is the force on the wire?

$F = BIL = 0.4 \times 2 \times 0.3 = 0.24\ \mathrm{N}$

Question 1

Which of the following best describes the direction of magnetic field lines around a bar magnet?

Accepted Answer

From south to north inside the magnet and from north to south outside the magnet.

Question 2

A straight conductor of length $0.5\ \mathrm{m}$ carries a current of $4\ \mathrm{A}$ and is placed at an angle of $30^\circ$ to a uniform magnetic field of flux density $0.2\ \mathrm{T}$. What is the magnitude of the force on the conductor?

Accepted Answer

$F = BIL\sin	heta = 0.2 	imes 4 	imes 0.5 	imes \sin 30^\circ = 0.2\ \mathrm{N}$

Question 3

Which rule is used to determine the direction of force on a current-carrying conductor in a magnetic field?

Accepted Answer

Fleming's Left Hand Rule

Question 4

A proton moves with velocity $v$ perpendicular to a uniform magnetic field $B$. What is the magnitude of the force acting on the proton?

Accepted Answer

$F = Bqv$

Question 5

A Hall probe is used to measure magnetic flux density. Which of the following factors does NOT affect the Hall voltage produced?

Accepted Answer

The resistance of the probe material

Question 6

In a velocity selector, charged particles pass through perpendicular electric and magnetic fields. If the electric field strength is $E$ and the magnetic flux density is $B$, what is the velocity of particles that pass through undeflected?

Accepted Answer

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

Question 7

Which of the following statements about the magnetic field around a straight current-carrying wire is correct?

Accepted Answer

The field lines form concentric circles centered on the wire.

Question 8

The magnetic flux density $B$ at a distance $r$ from a long straight wire carrying current $I$ is given by which equation?

Accepted Answer

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

Question 9

Two parallel wires carry currents in the same direction. What is the nature of the force between them?

Accepted Answer

They attract each other.

Question 10

A solenoid is wound with $N$ turns and carries a current $I$. What effect does inserting an iron core into the solenoid have?

Accepted Answer

It increases the magnetic field strength inside the solenoid.

Question 11

Which law states that the induced emf in a circuit is proportional to the rate of change of magnetic flux linkage?

Accepted Answer

Faraday's Law

Question 12

A coil of 100 turns encloses an area of $0.02\ \mathrm{m}^2$ and is placed in a uniform magnetic field of $0.5\ \mathrm{T}$. What is the total magnetic flux linkage?

Accepted Answer

$\lambda = N\Phi = 100 	imes 0.5 	imes 0.02 = 1\ \mathrm{Wb}$

Question 13

A bar magnet is moved into a coil, inducing an emf. According to Lenz's Law, what is the direction of the induced current?

Accepted Answer

It opposes the motion of the magnet.

Question 14

Which of the following best describes the Hall effect?

Accepted Answer

The production of a voltage across a conductor when it carries current in a magnetic field.

Question 15

A wire of length $0.3\ \mathrm{m}$ carries a current of $2\ \mathrm{A}$ and is placed perpendicular to a magnetic field of $0.4\ \mathrm{T}$. What is the force on the wire?

Accepted Answer

$F = BIL = 0.4 	imes 2 	imes 0.3 = 0.24\ \mathrm{N}$

Question 16

Which of the following is a correct expression for the induced emf according to Faraday's Law?

Accepted Answer

$\mathcal{E} = -\frac{\Delta (N\Phi)}{\Delta t}$

Question 17

A charged particle moves at right angles to a uniform magnetic field and follows a circular path. Which force provides the centripetal acceleration?

Accepted Answer

The magnetic force $F = Bqv$

Question 18

Which of the following changes will NOT increase the magnitude of the induced emf in a coil?

Accepted Answer

Increasing the resistance of the coil

Question 19

A rectangular coil is rotated in a uniform magnetic field. At which orientation is the induced emf maximum?

Accepted Answer

When the plane of the coil is parallel to the magnetic field lines

Magnetic Fields: Physics Study Notes (A-Level/College)

Study Guide - Practice Questions

Study Guide - Flashcards