10 minutes maximum! Can you do it in 5?

 1. Which of these diagrams shows the magnetic field line pattern (red lines) around a single straight wire carrying a current?

Magnetic field lines diagrams x4


2-4. The diagram shows a current carrying conductor in a magnetic field. wire with current in magnetic field - motor effect

2. Which law will predict the direction of the force on the wire?

  • A. The left hand grip rule.
  • B. The right hand grip rule.
  • C. Fleming's left hand rule.
  • D. Fleming's right hand rule.

3. In which direction will the wire be pushed?

  • A. Downwards.
  • B. Upwards.
  • C. To the right.
  • D. To the left.

4. The force on the wire is given by the formula F = B I L sinθ. The letter 'L' stands for....

  • A. the length of the wire within the magnetic field.
  • B. the total length of the wire.
  • C. the length of the magnet.
  • D. the length or distance between the 2 poles of the magnets.


5. The diagram shows a coil of wire with a current flowing through it in the direction shown by the arrows. The coil is between 2 magnets as shown.

coil in a magnetic field


Which way will the coil move?

  • A). Upwards.
  • B). Downwards.
  • C). Rotate clockwise.
  • D). Rotate anticlockwise.

6-8. An electron moves at a constant speed into a magnetic field as shown. (The dot/circle indicates the field is directed out of the screen).

electron entering a magnetic field


6. In which direction will the electron be pushed as it enters the field?

  • A. To the left.
  • B. To the right.
  • C. In to the screen.
  • D. Out of the screen.

7. The experiment is repeated with a proton of the same magnitude of charge and moving at the same velocity, but with a much higher mass than the electron, and the charge sign is positive.

Which of these statements is true for the size of the resulting force, compared to the force on the electron?

Magnitude of F Direction of F
The same Reversed
Increased Reversed
Increased The same
Decreased The same


8. Another electron moves upwards at constant speed, this time it is already within the field as shown.

electron already within magnetic field

Assuming the field covers a large area, which of these statements best describes the subsequent motion of the electron?

  • A). It is deflected 1800, and then follows a straight path through the field.
  • B). It moves round in a circle.
  • C). It is deflected 900, and then follows a straight path through the field.
  • D). A force acts, but it is not deflected.


9. What is the name of a long (empty) coil of wire used to produce a magnetic field?

  • A). A transformer
  • B). A potentiometer
  • C). A solenoid
  • D). An alternator

10. The Earth's magnetic field is of the order of 10-5 Tesla. To produce a force of 1 N on a wire of length 10 m (held perpendicularly to the field) the current flowing must be....

  • A). 10-6 A
  • B). 10-4 A
  • C). 10 4 A
  • D). 10 6 A