Static electricity: like charges push, unlike charges pull

Answer Key - Grade 8 Science Worksheet

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

1. 1.

   Both started neutral. After rubbing, Bo's balloon has 5 + and 9 − marks. The hair started with 8 + and 8 − marks. How many − marks does the hair have now?

   4 marks
2. 2.

   Both started neutral. After rubbing, Esme's balloon has 3 + and 6 − marks. The hair started with 8 + and 8 − marks. How many − marks does the hair have now?

   5 marks
3. 3.

   Jun holds a rubbed balloon near tiny paper bits, and the bits jump up to it. Why?

   • Rubbing made the balloon a magnet
   • The paper bits were already negative
   • The balloon's charge pulls on charges in the paper
   • Moving air lifts them
4. 4.

   Before the rubbed balloon comes near, what charge do the paper bits have, Kira?

   • Negative, like the balloon
   • None; they are neutral
   • Positive, or they could not be pulled
   • A north pole, like a magnet
5. 5.

   In the charge diagram, which side of the paper bit becomes slightly positive, Luz?

   • Both sides, since it is neutral
   • Neither, since neutral paper has no charges
   • The side away from the balloon
   • The side nearer the balloon

6. Read this first

   Paper-bit test (test results)

   distance (cm)	rubs on hair	paper bits picked up
   2	10	9
   5	10	4
   10	10	1
   2	5	5

7. 6.

   In the paper-bit test, what happens to the pull as the balloon is held farther away, Milo?

   • It gets weaker
   • It stays the same
   • It turns into a push
   • It gets stronger
8. 7.

   In the paper-bit test, what did 10 rubs do compared with 5 rubs, both at 2 cm, Noah?

   • Picked up half as many
   • Picked up fewer: more rubs remove charge
   • Picked up the same: rubs don't add charge
   • Picked up more: more charge, stronger pull
9. 8.

   Pia wants to test only distance, fairly. What must stay the same in each try?

   • Nothing, since rubs don't change the charge
   • The distance from the paper
   • The number of rubs
   • Nothing, since distance doesn't change the pull
10. 9.

    Does rubbing a balloon on hair make new charge, Tala?

    • Yes, rubbing makes electrons
    • Yes, it moves protons into the balloon
    • No, it moves electrons between them
    • Yes, rubbing makes protons
11. 10.

    Why does a rubbed balloon stick to a wall, Zee?

    • The balloon turns into a magnet
    • The wall makes new charge from the air
    • Its charge pulls on charges in the wall
    • Rubbing makes the balloon sticky