(a) The diagram shows a negatively charged plastic rod held close to a thin stream of water. The water is attracted towards the rod.

Which one of the following statements explains what is happening to the charge in the water?

• The positive and the negative charges in the water are attracted to the rod.
• The positive and the negative charges in the water are repelled by the rod.
• The negative charge in the water is repelled by the rod and the positive charge is attracted.
• The negative charge in the water is attracted by the rod and the positive charge is repelled.

(1 mark)

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(b) A company that produces bottles of mouthwash found a problem with the automatic filling system.

As the bottles go towards the filler, they move around on the conveyer belt and become electrostatically charged. This causes the stream of mouthwash to move sideways, missing the open top of the bottle.

The company came up with a solution to the problem. Before the bottles reach the filler, they pass through a stream of ionised air. The ions in the air neutralise the charge on the bottles.

(b) (i) Explain why the plastic bottles become charged.

(2 marks)

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(b) (ii) What is an ion?

(1 mark)

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(b) (iii) Earthing the conveyor belt with a conducting wire would not have solved this problem.
Give a reason why.

(1 mark)

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