Magnetism and Electromagnetic Induction MCQs

Question 1

MRI scanners use very strong magnetic fields produced by:

Accepted Answer

superconducting solenoids

Answer

bar magnets

Answer

static charges

Answer

solar cells

Question 2

In a transformer, the secondary coil's flux linkage depends on:

Accepted Answer

its number of turns and the flux in the core

Answer

the primary's resistance

Answer

the colour of the wire

Answer

only its resistance

Question 3

When the ground shakes, the magnet (fixed to the frame) moves while the coil:

Accepted Answer

tends to stay still because of its inertia

Answer

moves with exactly the same motion

Answer

disappears

Answer

vibrates faster

Question 4

A coil's flux is 0.03 Wb. If the field doubles and the area halves, the flux becomes:

Accepted Answer

0.03 Wb

Answer

0.06 Wb

Answer

0.015 Wb

Answer

0.12 Wb

Question 5

Which change does NOT alter the flux through a coil?

Accepted Answer

sliding the coil sideways within a uniform field (same orientation)

Answer

changing the coil's area

Answer

rotating the coil

Answer

changing the field strength

Question 6

Which quantity is measured in teslas?

Accepted Answer

magnetic flux density

Answer

magnetic flux

Answer

inductance

Answer

induced e.m.f.

Question 7

A beam of electrons in a TV tube is deflected by magnetic coils because:

Accepted Answer

the moving electrons experience F = Bqv

Answer

the electrons are stationary

Answer

the electrons are attracted by gravity

Answer

the coils heat the electrons

Question 8

An alpha particle (charge 2 1.6 10^-19 C) moves at 1 10^7 m/s at 90^circ to a field of 1.5 T. The magnetic force on it is:

Accepted Answer

4.8 10^-12 N

Answer

2.4 10^-12 N

Answer

9.6 10^-12 N

Answer

4.8 10^-11 N

Question 9

The force on a current-carrying wire is a result of forces on:

Accepted Answer

the moving charges (electrons) inside it

Answer

the protons in the wire

Answer

the insulation

Answer

the air

Question 10

Where magnetic field lines are close together, the field is:

Accepted Answer

strong

Answer

weak

Answer

reversed

Answer

zero

Question 11

Which change would increase the force on a current-carrying wire in a magnetic field?

Accepted Answer

increasing the current

Answer

reducing the field

Answer

turning the wire parallel to the field

Answer

reducing the length in the field

Question 12

A flux density of 1.2 T passes perpendicularly through an area of 0.002 m^2. The magnetic flux is:

Accepted Answer

0.0024 Wb

Answer

0.0048 Wb

Answer

2.4 10^-4 Wb

Answer

0.024 Wb

Question 13

The forces that two parallel wires exert on each other are:

Accepted Answer

equal and opposite (Newton's third law)

Answer

in the same direction

Answer

zero

Answer

unequal

Question 14

The field of a solenoid with an iron core may be hundreds of times stronger because iron has:

Accepted Answer

a high relative permeability

Answer

low density

Answer

a low melting point

Answer

high resistivity

Question 15

An electron moves at 3 10^6 m/s perpendicular to a 0.002 T field. The radius of its circular path is (m = 9.11 10^-31 kg, q = 1.6 10^-19 C):

Accepted Answer

0.00854 m

Answer

0.0171 m

Answer

8.54 10^-4 m

Answer

0.0854 m

Question 16

Seismometers in many places record arrival times of waves to:

Accepted Answer

locate the earthquake's origin

Answer

predict rain

Answer

measure gravity waves

Answer

measure the Sun's temperature

Question 17

Unlike electric field lines, magnetic field lines:

Accepted Answer

form closed loops

Answer

start and end on charges

Answer

are always straight

Answer

are radial

Question 18

A wire of length 0.3 m carries 5 A at 90^circ to a uniform magnetic field of 0.2 T. The force on it is:

Accepted Answer

0.3 N

Answer

0.4 N

Answer

0.15 N

Answer

0.6 N

Question 19

Two parallel wires carrying currents in the same direction:

Accepted Answer

attract each other

Answer

rotate

Answer

repel each other

Answer

exert no force

Question 20

The time for one revolution of a charged particle in a magnetic field is:

Accepted Answer

T = 2pi mBq

Answer

T = mBqv

Answer

T = 2pi rBq

Answer

T = Bq2pi m

Question 21

A 0.3 m rod moves at 5 m/s across a 0.4 T field on rails joined by a 2 Ω resistor. The induced current is:

Accepted Answer

0.3 A

Answer

1.2 A

Answer

0.6 A

Answer

3 A

Question 22

An MRI scanner field of 3 T is about how many times the Earth's field (~50 μT)?

Accepted Answer

6 10^4

Answer

6 10^-5

Answer

150

Answer

60

Question 23

Iron filings sprinkled round a magnet show:

Accepted Answer

the pattern of the magnetic field lines

Answer

the temperature

Answer

the electric field

Answer

the gravitational field

Question 24

When the current in an electromagnet with a soft-iron core is switched off:

Accepted Answer

the core loses most of its magnetism

Answer

the core melts

Answer

the poles swap

Answer

the core becomes strongly magnetised

Question 25

1 T = 1 Wb m^-2 shows that flux density is:

Accepted Answer

flux per unit area

Answer

area per unit flux

Answer

flux times area

Answer

force per charge

Magnetism and Electromagnetic Induction MCQs — Physics (page 5)

101. MRI scanners use very strong magnetic fields produced by:

102. In a transformer, the secondary coil's flux linkage depends on:

103. When the ground shakes, the magnet (fixed to the frame) moves while the coil:

104. A coil's flux is 0.03 Wb. If the field doubles and the area halves, the flux becomes:

105. Which change does NOT alter the flux through a coil?

106. Which quantity is measured in teslas?

107. A beam of electrons in a TV tube is deflected by magnetic coils because:

108. An alpha particle (charge 2 1.6 10^-19 C) moves at 1 10^7 m/s at 90^circ to a field of 1.5 T. The magnetic force on it is:

109. The force on a current-carrying wire is a result of forces on:

110. Where magnetic field lines are close together, the field is:

111. Which change would increase the force on a current-carrying wire in a magnetic field?

112. A flux density of 1.2 T passes perpendicularly through an area of 0.002 m^2. The magnetic flux is:

113. The forces that two parallel wires exert on each other are:

114. The field of a solenoid with an iron core may be hundreds of times stronger because iron has:

115. An electron moves at 3 10^6 m/s perpendicular to a 0.002 T field. The radius of its circular path is (m = 9.11 10^-31 kg, q = 1.6 10^-19 C):

116. Seismometers in many places record arrival times of waves to:

117. Unlike electric field lines, magnetic field lines:

118. A wire of length 0.3 m carries 5 A at 90^circ to a uniform magnetic field of 0.2 T. The force on it is:

119. Two parallel wires carrying currents in the same direction:

120. The time for one revolution of a charged particle in a magnetic field is:

121. A 0.3 m rod moves at 5 m/s across a 0.4 T field on rails joined by a 2 Ω resistor. The induced current is:

122. An MRI scanner field of 3 T is about how many times the Earth's field (~50 μT)?

123. Iron filings sprinkled round a magnet show:

124. When the current in an electromagnet with a soft-iron core is switched off:

125. 1 T = 1 Wb m^-2 shows that flux density is:

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