(a) State the two types of electric charge. [1 mark]
(b) State the rule that describes which charges attract and which repel. [1 mark]
For each pair of charges below, state whether they attract or repel. [3 marks]
(a) A positive charge and another positive charge:
(b) A negative charge and another negative charge:
(c) A positive charge and a negative charge:
When a solid is charged by friction (rubbing), what is transferred from one object to the other, and is its charge positive or negative? [2 marks]
Define each of the following terms. [2 marks]
(a) An electrical conductor:
(b) An electrical insulator:
State the unit used to measure electric charge, and give its symbol. Supplement [1 mark]
Describe a simple experiment to produce an electrostatic charge by friction, and a simple way to detect that the object is charged. [4 marks]
A polythene rod is rubbed with a wool cloth. After rubbing, the polythene rod has a negative charge and the wool has a positive charge. Explain, in terms of electrons, how this happens. [3 marks]
Describe an experiment you could carry out to find out whether a material is an electrical conductor or an insulator. State clearly what you would observe in each case. [4 marks]
Using a simple electron model, explain why a metal such as copper is a good electrical conductor, while plastic is an insulator. Give one further typical example of each. [4 marks]
Supplement
(a) Describe what is meant by an electric field. [1 mark]
(b) State what is meant by the direction of an electric field at a point. [2 marks]
This question is about charging solids by friction.
(a) Explain why charging a solid by friction involves only a transfer of negative charge, and not a movement of positive charge. [2 marks]
(b) A Perspex rod is rubbed with a wool cloth. The Perspex becomes positively charged. Explain, in terms of electrons, how this happens and what charge the wool gains. [3 marks]
(c) During this rubbing, is any charge created or destroyed? Explain your answer. [1 mark]
This question is about the forces between charges.
(a) Two identical plastic rods are each rubbed with wool, and both become negatively charged. State and explain what happens when one rod is brought close to the other. [2 marks]
(b) A charged rod is held near a thin stream of water from a tap. The water bends towards the rod. What does this tell you about the rod? [1 mark]
(c) A positively charged rod is brought near a negatively charged sphere. State whether they attract or repel. [1 mark]
A student tests four materials in a circuit that contains a cell and a lamp. The results are shown in the table.
| Material | Lamp lights? |
|---|---|
| Copper wire | Yes |
| Plastic ruler | No |
| Iron nail | Yes |
| Rubber band | No |
(a) Use the results to classify each material as a conductor or an insulator. [2 marks]
(b) Using the simple electron model, explain the difference between the materials that let the lamp light and those that did not. [2 marks]
(c) Give one further typical example of a conductor and one of an insulator that are not in the table. [2 marks]
This question is about electric field patterns. Supplement
(a) In the space below, sketch the electric field pattern around a single positive point charge. Include arrows to show the direction of the field. [2 marks]
(b) Describe the electric field pattern around a negatively charged conducting sphere, including the shape of the lines and their direction. [2 marks]
This question is about the field between two oppositely charged parallel plates. Supplement
(a) In the space below, sketch the electric field pattern in the region between two oppositely charged parallel plates. Give two features of the field lines you have drawn. [3 marks]
(b) State the direction of the field between the plates. [1 mark]
(c) Explain how you could use a small positive charge to find the direction of an electric field at a point. [2 marks]
