Static electricity: like charges push, unlike charges pull

Answer Key - Grade 8 Science Worksheet - Challenge Me

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

1. 1.

   Two balloons rubbed on Ari's neutral hair gain 3 and 4 electrons. The hair started with 12 − marks. How many − marks does the hair have now?

   5 marks
2. 2.

   Two balloons rubbed on Esme's neutral hair gain 4 and 3 electrons. The hair started with 14 − marks. How many − marks does the hair have now?

   7 marks

3. Read this first

   Balloon-and-hair pairs (example data)

   pair	extra charges on each	distance apart (cm)
   A	2	10
   B	6	2
   C	6	10
   D	2	2

4. 3.

   In the table of pairs, which pair pulls together hardest, Jun?

   • D, since distance alone decides it
   • C, since charge alone decides it
   • A, since far apart pulls harder
   • B
5. 4.

   In the table of pairs, which pair pulls together most weakly, Kira?

   • C, since it is farthest apart
   • A
   • D, since it has the least charge
   • B, since close pairs pull weakly
6. 5.

   Milo says rubbing a balloon on hair makes new charge. Agree or disagree?

   • Agree: rubbing creates electrons
   • Agree: rubbing magnetizes the balloon and the hair
   • Agree: protons rub off the balloon
   • Disagree: electrons just move to the balloon
7. 6.

   Noah says a balloon sticks to the wall because rubbing makes it a magnet. Agree or disagree?

   • Disagree: its electric charge pulls the wall
   • Agree: the balloon gets a north pole
   • Agree: protons in the wall jump to it
   • Agree: neutral walls can't feel a charge
8. 7.

   Pia says a rubbed balloon can only pull on objects that are already charged. Agree or disagree?

   • Agree: the balloon has to touch them
   • Agree: the paper must make its own charge first
   • Disagree: neutral paper bits get pulled too
   • Agree: neutral things feel no pull
9. 8.

   Ren wants to test whether more rubbing gives a stronger pull on paper bits. Which plan is fair?

   • Change the rubs and the distance together
   • Change the rubs; keep the distance the same
   • Keep the rubs the same; change the distance
   • Use a magnet in place of the balloon
10. 9.

    Two balloons rubbed on hair push each other away, but each one pulls on the hair. Why, Tala?

    • The hair is a weak magnet
    • The balloons are both −; the hair is +
    • The balloons lost their charge
    • Rubbing made new charge in the hair
11. 10.

    Zee holds a rubbed balloon near a thin stream of circle water, and the stream bends toward it. What does that show?

    • The water stream is a magnet
    • Neutral water can't be pulled
    • A charge can pull neutral water without touching
    • The balloon makes new charge in the water