Charge, potential difference, energy

and current

1. 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)

2. 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)

3. For one of the above examples, describe how the process works. ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….(4 marks)

4. What is the equation that links charge, current and time? Q = It ...................................................(1mark)

5. What is the equation that links charge, potential difference and energy? E = QV................................(1 mark)

6. How much charge flows when a current of 2A flows for 30 seconds? ..............................60C........................(1mark)

7. What current flows if a charge of 300C flows for 3minutes? ……………………1.7A....................................(1 mark)

8. What current flows if a charge of 270C flows for 106seconds? …………………2.5A…………………………………….(1 mark)

9. A p.d. of 12V is applied across a resistor. 250C of charge passes. How much energy was dissipated by the resistor ? …...............................3000J.........................................(1 mark)

10. A current of 0.12A flows through a resistor which has a resistance of 150 Ohms, 300C of charge passes. How much energy was dissipated by the resistor? V = IR V = 18..18x300 = 5400J.............................(2 marks)

11. A light bulb releases 230J of energy when connected to a 11V battery. How much charge flowed in the circuit? …………………20.9C………………………………….……(1 mark)

The diagram shows a charged thundercloud.

(a) Why does the tree below the thundercloud become positively charged?electrons / negative charges areRepelled (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) = potentialdifference × 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 lightningstrike. Show clearly how you work out your answer.......E = VQ = 1200000 x 18 = 21600000000..........Maximum energy transferred =21 600 000 000 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.copper is a good (electrical)conductor or copper has a lowResistance (1 mark) ......................................................................................................... provides path for electrons /electricity / lightning to earth /ground / metal plate (1 mark)