 µ IB | Magnetic Fields

10 quick questions

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? 2-4. The diagram shows a current carrying conductor in a magnetic field. 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 direcion shown by the arrows. The coil is between 2 magnets as shown. Which way will the coil move?

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

6-8. An electron is directed into a magnetic field as shown. (The dot/circle indicates the field is directed out of the screen). 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 A The same Reversed B Increased Reversed C Increased The same D Decreased The same

8. An electron moves at constant speed within a uniform field that covers a large area. initially the electron is moving upwards again. 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 and 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