Forces between charged and uncharged objects
4 marks · NormalA student hangs a thin strip of aluminium foil from a wooden support. The foil is initially uncharged. She brings a charged rod near it and observes the foil moving towards the rod.
Describe what type of force acts between the charged rod and the uncharged foil.
Explain, in terms of charge, how the uncharged foil is able to be attracted to the charged rod.
State what happens if the foil and the rod become similarly charged and the rod is brought near again.
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.
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(a) Attractive force (electrostatic attraction)
(b) The charged rod induces an opposite charge on the near side of the foil, so the foil is attracted to the rod.
(c) The foil will be repelled/move away.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States attractive force or electrostatic attraction
B2 (b) · 1 mark · Explains that charge is induced on the foil
B3 (b) · 1 mark · Opposite charges attract (clear reasoning)
B4 (c) · 1 mark · States that the foil is repelled/moves away
Worked solution
(a) There is an attractive force between the charged rod and the uncharged foil.
(b) The charged rod induces an opposite charge on the near side of the foil, causing the foil to be attracted to the rod.
(c) If the foil and rod are similarly charged, the foil will be repelled and move away.