1) 1 kW = ? W a) 100 b) 10 c) 1000 2) 800 W = kW a) 0.8 b) 8 c) 800 3) A hairdryer with a power of 1kW is used for 30 s. Calculate the electrical energy needed. a) 30 J b) 30 000 J c) 3000 J 4) An electric hot plate uses 8000 J of energy in 4 s. Calculate the power. a) 2000 kW b) 2000 W c) 32 000 W 5) A 800 W kettle is connected to the 240 V mains supply. Calculate the current. a) 3.33 A b) 3.33 V c) 3.33 ohms 6) The interior light of a car has a current of 2A in it. The voltage across it is 12V. What is the electrical power used by the light? a) 6 W b) 0.2 W c) 24 W 7) Electricity costs 20 cents per kilowatt-hour. What is the cost of using a 0.5kW heater for ten hours? hours? a) $100 b) $10 c) $1 8) Electrical energy costs 30 cents for 1 kWh. How much does it cost to use a 6000 W oven for 4 hours? 4 hours? a) $7.20 b) $720 000 c) $72

Electricity Formulas

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