A student investigates static electricity using an acrylic rod and a polyester cleaning cloth.
Explain in terms of electrons why the acrylic rod is not normally charged.
Explain in terms of electrons why the acrylic rod becomes charged when the student rubs it with the polyester cloth.
The diagram shows the electric field between two charges, X and Y.

State the charges of X and Y.
Use the diagram to explain your answer.
Describe one similarity between the electric field line diagram and a magnetic field line diagram for a bar magnet.
Calculate the charge when 432 J of energy is transferred with a potential difference of 18 V.
Use the equation:
energy transferred=charge×potential difference \text{energy transferred} = \text{charge} \times \text{potential difference} energy transferred=charge×potential difference