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GCSE Questions: Static Electricity

Q4.

(a)    The diagram shows a negatively charged plastic rod held near 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?

A) The positive and the negative charges in the water are attracted to the rod.  

B) The positive and the negative charges in the water are repelled by the rod.

C) The negative charge in the water is repelled by the rod and the positive charge is attracted to the rod.

D) The negative charge in the water is attracted to the rod and the positive charge is repelled by the rod.

[1 mark]

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

As the bottles go towards the filler, the bottles move around on the conveyor 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 an answer to the problem. Before the bottles reach the filler, the bottles pass through a stream of ionised air. The ions in the air neutralise the charge on the bottles.

(i)      Explain why the plastic bottles became charged.

Friction as the bottles rub between the bottles and conveyor belt (and/or plastic guides) causes electrons to transfer onto (or off - no detail is given of the type of material used for the bottles) the bottles.

Only electrons are transferred - any mention of protons or neutrons moving will result in no mark being awarded!

(ii)     What happens to the structure of an atom to change the atom into an ion?

It gains or loses electrons.

(iii)     Simply earthing the conveyor belt with a conducting wire would not have solved this problem.

Give a reason why this would not work.

Charge will not (easily) flow off the conveyor belt and it is made of a good insulator (rubber).

For an earthing wire to work the charge accumulated on the equipment would have to flow freely to the wire. The equipment would need to be made of a metal. Also the charge on the bottles themselves would not necessarily ransfer to the conveyor belt. Whenever everything is made of insulating materials it is likely movement will result in a build up of static charge.

The ionised air would be attracted to the oppositely charged build up of charge on the bottles and would neutralise the charge build up.

 

[Total 5 marks]