O-LevelPhysicsElectricity5054/22 · Oct/Nov 2018 · Q56 Marks

Two uncharged conducting spheres, K and L, are mounted on insulating stands.

(a)State how the structure of an insulator differs from that of a conductor and give one example of an insulator.[2]
(b)(i)The two spheres are in contact. Fig. 5.1 shows a positively-charged insulating rod held next to K. On Fig. 5.1, draw the charges on K and on L. [Figure 5.1][2]
(b)(ii)1Sphere L is moved to the right, a long way from sphere K. The positively charged rod is moved away. State what happens to the charge on K.[1]
(b)(ii)2An earthing wire is connected to sphere L. State what happens to the charge on L.[1]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2018). The mark or mark type is shown in brackets.

[1] charges / electrons are not free to move (in an insulator)
[1] any sensible example e.g. plastic / nylon / glass / rubber
[1] negative charge on left of K and positive charge on right of L
[1] equal numbers of charges and number < 5 and no charges on right of K and no charges on left of L
[1] (negative) charge spreads throughout (surface of) sphere
[1] (positive) charge on L disappears or L becomes neutral or equal number of positive and negative charges

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