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

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

   • 2.8125 μJ
   • 5.625 μJ
   • 11.25 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?

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

   A compass needle is turned away from north and let go. Why does it swing back, Noah?

   • Its battery turns it
   • Field energy turns into its motion
   • Air pushes it back
10. 9.

    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 decreases
    • It increases
    • It stays the same
11. 10.

    A proton is released near the positive plate. Which way does it move, Tala?

    • Toward the negative plate
    • It stays put
    • Toward the positive plate