Energy changes when charges or magnets move in a field

Answer Key - Grade 11 Science Worksheet

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

1. 1.

   Like charges of 15 nC and 40 nC sit 6 cm apart. With k = 8.9875 × 10⁹ N·m²/C², how much energy is stored, in μJ, to 0.01, Ari?

   89.88 μJ
2. 2.

   Like charges of 25 nC and 40 nC sit 4 cm apart. With k = 8.9875 × 10⁹ N·m²/C², how much energy is stored, in μJ, to 0.01, Bo?

   224.69 μJ
3. 3.

   Like charges of 10 nC and 10 nC sit 2 cm apart. With k = 8.9875 × 10⁹ N·m²/C², how much energy is stored, in μJ, to 0.01, Esme?

   44.94 μJ

4. Read this first

   Energy stored by two like charges at different distances (example data)

   Distance (cm)	Stored energy (μJ)
   2	45
   4	22.5
   8	11.25
   16	?

5. 4.

   Using the table, what happens to the stored energy each time the distance doubles, Jun?

   • It halves
   • It doubles
   • It drops to one-quarter
6. 5.

   Using the table, what energy should be stored at 16 cm, Kira?

   • 11.25 μJ
   • 5.625 μJ
   • 2.8125 μJ
7. 6.

   Using the table, the charges are released at 2 cm. What happens, Luz?

   • Nothing, since they are at rest
   • They fly apart, gaining kinetic energy
   • They pull together
8. 7.

   A magnet is pulled off a steel fridge door. Where does the work done go, Milo?

   • It is destroyed
   • Into making the fridge door colder
   • Into the magnetic field's energy
9. 8.

   A toy train floats above a track on repelling magnets. What happens to the field energy if the train is pushed down closer, Pia?

   • It stays the same
   • It decreases
   • It increases
10. 9.

    An electron is released between a positive and a negative metal plate. What happens to its kinetic energy as it moves, Ren?

    • It decreases
    • It stays at zero
    • It increases
11. 10.

    As a charge speeds up between the plates, what happens to the stored field energy, Zee?

    • It rises by the same amount
    • It stays the same
    • It drops by the kinetic energy gained