Charge potential difference energy and current 1 2

Charge, potential difference, energy and current

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. What does it mean if something is described as charged? the object has a net positive or negative charge due to electrons being taken away or given to the object (2 marks) List 3 ways that static electricity is used in industry? Any three from: Electrostatic precipitator (smoke scrubbers in chimneys). Photocopiers. Printers. Powder coating/spraying. (3 marks) For one of the above examples, describe how the process works. ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………. (4 marks) What is the equation that links charge, current and time? Q = It. . . . (1 mark) What is the equation that links charge, potential difference and energy? E = QV. . . . (1 mark) How much charge flows when a current of 2 A flows for 30 seconds? . . . . 60 C. . . (1 mark) What current flows if a charge of 300 C flows for 3 minutes? ………… 1. 7 A. . . . . (1 mark) What current flows if a charge of 270 C flows for 106 seconds? ………………… 2. 5 A…………………. (1 mark) A p. d. of 12 V is applied across a resistor. 250 C of charge passes. How much energy was dissipated by the resistor ? …. . . . 3000 J. . . . . (1 mark) A current of 0. 12 A flows through a resistor which has a resistance of 150 Ohms, 300 C of charge passes. How much energy was dissipated by the resistor? V = IR V = 18. . 18 x 300 = 5400 J. . . . (2 marks) A light bulb releases 230 J of energy when connected to a 11 V battery. How much charge flowed in the circuit? ………………… 20. 9 C…………………. ……(1 mark)

The diagram shows a charged thundercloud. (a) Why does the tree below the thundercloud become positively charged? electrons / negative charges are Repelled (1 mark) (b) The base of the cloud has a negative charge of 18 coulombs. The potential difference between the base of the cloud and the ground is 1 200 000 kilovolts. (i) Write down the equation that links charge, energy transferred and potential difference. energy (transferred) = potential difference × charge (accept E = V × Q, accept W = V × Q) (1 mark)

(ii) Calculate the maximum energy that could be transferred to the ground by a lightning strike. Show clearly how you work out your answer. . . . E = VQ = 1200000 x 18 = 2160000. . Maximum energy transferred =21 600 000 or 2. 16 × 1010 joules (2 marks) (c) A lightning conductor is usually attached to tall buildings. This reduces the risk of damage by a lightning strike. Explain why the lightning conductor is made of copper is a good (electrical) conductor or copper has a low Resistance (1 mark). . . . . . . provides path for electrons / electricity / lightning to earth / ground / metal plate (1 mark)