Question 1

The diagram shows a clockwise current I in a circular coil placed in a uniform magnetic field B with the plane of the coil perpendicular to the magnetic field.

What is the effect on the coil of the interaction between the current and the magnetic field?

  A  

it rotates about the axis with the top moving out of the page

  B  

it rotates about the axis with the top moving into the page


  C  

it causes an increase in the diameter of the coil

  D  

it causes a decrease in the diameter of the coil


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Question 2

Charged particles, each of mass m and charge Q, travel at a constant speed in a circle of radius r in a uniform magnetic field of flux density B. 

Which expression gives the frequency of rotation of a particle in the beam?

2 π mB Q​
mB Q​
π mB Q​
m2 π B Q​

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Question 3

When an electron is moving at a speed v perpendicular to a uniform magnetic field of flux density B, it follows a path of radius R.

A second electron moves at a speed v2\frac{v}{2} perpendicular to a uniform magnetic field of flux density 4B.

What is the radius of the path of the second electron?

8R​
4R​
2 R
8 R

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Question 4

Different magnetic fields are present in the two chambers shown. A particle enters the first chamber at a velocity of

80 m s–1 and is deflected into a circular path of radius 200 mm. In the second chamber it follows a circular path of radius 100 mm.

The particle leaves the second chamber at a speed of

  A  

20 m s–1

  B  

40 m s–1

  C  

80 m s–1

  D  

160 m s–1

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Question 5

A charged particle moves in a circular path of radius 1.2cm in a uniform magnetic field.

The direction of the magnetic field is perpendicular to the plane of the paper.

The particle has mass m, charge +Q and speed v.

Another particle of mass 3m, charge +2Q and speed v moves in a circular path of radius R in the same magnetic field.

What is the value of R?

  A  

0.8 cm

  B  

1.2 cm

  C  

1.8 cm

  D  

7.2 cm

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Question 6

An electron moves in a circle of radius 2.0 cm in a uniform magnetic field of flux density 170 mT.

What is the momentum of this electron?

  A  

3.4 × 10−3 kg m s−1


  B  

5.4 × 10−17 kg m s−1


  C  

1.4 × 10−18 kg m s−1


  D  

5.4 × 10−22 kg m s−1


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Question 7

A beam of charged particles is not deflected when it passes through a region where both electric and magnetic fields are present.

Which statement is not correct?

  A  

all the particles have the same speed

  B  

the resultant force on each particle is zero

  C  

the magnetic force is equal to the electric force on each particle

  D  

the magnetic field and the electric field are in the same direction


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Question 8

A horizontal wire of length 0.50 m and weight 1.0 N is placed in a uniform horizontal magnetic field of flux density 1.5 T directed at 90° to the wire.

What is the current that just supports the wire?

  A  

0.33 A

  B  

0.75 A

  C  

1.3 A

  D  

3.0 A

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Question 9

The graph shows how the flux linkage, NФ, through a coil changes when the coil is moved into a magnetic field.

The emf induced in the coil

  A  

decreases then becomes zero after time t0

  B  

increases then becomes constant after time t0

  C  

is constant then becomes zero after time t0

  D  

is zero then increases after time t0


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