10.3 B Direct current work and power of current Power

Power Calculations

1.      What is the power rating of a light bulb that transfers 120 joules of energy in 2 seconds? 60W

2.      A fridge uses 540,000J of electrical energy in 1 hour. What is its power rating? 150W

3.      A modem uses 10,000J of energy in 30 minutes. What is its power rating? 5.5W

4.      A colour television has a power rating of 150 Watts. How much electrical energy dose2 it use when you forget to turn it off for 4 hours? 2160000 J

5.      A 3kW kettle boils water in 4 minutes.  Does this use more electrical energy than a 150W fridge left on for 1 hour? Kettle 720000J Fridge 540000J

6.      What is the potential difference when a current of 0.8A flows through a cooker with a wattage of 2300W? 2875V

7.      A Fridge Freezer operates with a potential difference of 230V when a current of 1.6A flows, what is the power rating for this appliance. 368W

8.      A computer screen runs with a resistance of 120 Ohms and a current of 0.4 amps what is the power rating. 19.2W

9.      A fan has a power rating of 40W with a current of 0.6 Amps what is the resistance. 111.11 Ohms

10.  A potential difference of 110V is required to transfer energy to a drill with a current of 0.8A what is its power rating.  88W

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