Electric Charge
4 marks · EasyA student uses a plastic rod and a small piece of paper in an investigation. After rubbing the rod, he observes the paper is attracted to the rod. In another experiment, the rod is brought close to another charged rod, and they repel each other.
State one property that both the plastic rod and the paper must have for the first experiment to work.
Describe how the small piece of paper is attracted to the charged rod, even though the paper is uncharged at first.
Explain why the two rods repel each other in the second experiment.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Both must be electrical insulators.
(b) The charged rod induces opposite charges on the near side of the paper, causing attraction; this is called induced charge.
(c) The rods have like charges and so repel each other due to electrostatic repulsion.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States both are insulators.
M1 (b) · 1 mark · Explains induced charge or redistribution of charges on the paper.
A1 (b) · 1 mark · States attraction occurs due to opposite induced charges.
B2 (c) · 1 mark · States like charges repel or explains rods have same charge.
Worked solution
a) Both must be electrical insulators to become charged by friction.
b) The charged rod causes electrons in the paper to move slightly, inducing opposite charge on the closer side, which creates attraction.
c) Both rods have the same type of charge, so they repel each other.