1. 1
   On a dry winter's day, a person rubs a plastic comb with a woollen cloth and finds that the comb attracts small pieces of paper afterwards.

   (a)

   A plastic comb is rubbed with a dry cloth and becomes negatively charged. What has happened to cause this?

   [1 mark]

   • AProtons have moved from the cloth to the comb
   • BElectrons have moved from the cloth to the comb
   • CElectrons have moved from the comb to the cloth
   • DNeutrons have moved from the comb to the cloth

   (b)

   After being rubbed and losing electrons, what overall charge does the woollen cloth have?

   [1 mark]

   • APositive
   • BNegative
   • CNo overall charge
   • DIt cannot be charged

   (c)

   Explain why the charged comb is able to attract small, uncharged pieces of paper.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   During refuelling at an airport, friction between fuel and the inside of a pipe can cause a fuel tanker to build up a static electric charge. Engineers attach an earthing cable between the tanker and the aircraft before refuelling begins.

   (a)

   A fuel tanker becomes positively charged through friction as fuel flows through its pipes during delivery. What type of force would this charge exert on another positively charged object nearby?

   [1 mark]

   • AAttraction
   • BA magnetic force only
   • CNo force
   • DRepulsion

   (b)

   What is the main danger if a charged fuel tanker is not earthed before refuelling begins?

   [1 mark]

   • AThe fuel could evaporate faster
   • BThe tanker's engine could stop working
   • CA spark could occur and ignite flammable fuel vapour
   • DThe fuel would become magnetic

   (c)

   Explain, in terms of electron transfer, how connecting an earthing cable between the tanker and the aircraft reduces the risk of a spark occurring.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A Victorian scientist demonstrating static electricity to a public audience charges an isolated metal sphere by rubbing it repeatedly, then asks a volunteer to bring a small charged rod close to the sphere without touching it, causing a visible spark to jump across the gap.

   (a)

   A Victorian scientist demonstrating static electricity to an audience rubs an isolated metal sphere so that it gains a uniform negative charge. Sketch in words the electric field pattern around the isolated charged sphere, describing its shape and direction.

   [3 marks]

   (b)

   Explain why a visible spark can jump between the charged sphere and the charged rod when they are brought close together without touching.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   An engineer is investigating why workers at a grain storage facility, where fine dry grain dust is blown through metal ducts, are at risk of dust explosions caused by static sparks building up from friction between the dust and the duct walls.

   (a)

   Explain, in terms of electron transfer and electric fields, how repeated friction between the grain dust and the ducts can lead to the build-up of static charge, and how this charge can eventually cause a spark.

   [6 marks]

   (b)

   The engineer proposes bonding all the metal ducts together with conducting wire and connecting them to an earthing rod. Evaluate how effective this proposal would be at reducing the risk of static sparks in the grain storage facility, explaining your reasoning in terms of charge transfer.

   [6 marks]

   Total for question 4: 12 marks

End of questions