Magnetic force on moving charges, and how motors work

Answer Key - Grade 11 Science Worksheet - Challenge Me

Circle the best answer, or write your answer on the line.

1. 1.

   A motor coil has 40 turns, and each side has 0.04 m in a 0.25 T field. It carries 0.5 A. What force acts on one side, Ari?

   0.2 N
2. 2.

   A motor coil has 100 turns, and each side has 0.05 m in a 0.1 T field. It carries 0.8 A. What force acts on one side, Bo?

   0.4 N
3. 3.

   A motor coil has 25 turns, and each side has 0.03 m in a 0.4 T field. It carries 1.2 A. What force acts on one side, Esme?

   0.36 N
4. 4.

   A proton moves straight across a magnetic field. What does the field do to its path, Jun?

   • Leaves it unchanged
   • Bends it into a curve
   • Speeds it up in a straight line
5. 5.

   A magnetic force keeps bending a moving electron's path. What happens to its speed, Luz?

   • It keeps rising
   • It keeps falling
   • It stays the same
6. 6.

   Milo says a wire lying along magnetic field lines feels the biggest force. Agree or disagree?

   • Disagree: it feels none
   • Agree: along the field is strongest
   • Agree: the field pushes it along
7. 7.

   Noah says a current running along a field still gets pushed sideways. Agree or disagree?

   • Agree: any current in a field is pushed
   • Disagree: it must cross the field
   • Agree: fields push along their lines
8. 8.

   Pia says a simple motor would spin the same way without its commutator. Agree or disagree?

   • Agree: the commutator is just decoration
   • Disagree: it would rock back and forth
   • Agree: the magnet keeps it spinning
9. 9.

   What part of an electric fan makes the blades turn, Tala?

   • A light bulb
   • A battery alone
   • A motor
10. 10.

    A toy car's motor is wired to its battery the other way round. What happens, Zee?

    • It drives the other way
    • It stops and won't start again
    • It drives faster