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# Electricity Current Voltage and Power Problems

Power is the rate of doing work. The units for power are Joules per second, Js-1 or Watts, W.To calculate power we use the following formula:

Power = Voltage x Current

Calculate the following problems to determine the unknowns.

1. The voltage across household light bulbs is 240 V. The current is 0.42 A. Calculate the bulbs power output in Watts. 2. A 2 kW heater is operating at 240 V. Determine the current it is drawing from mains power
supply.

1. A 2kW heater is operating at 240V. Determine the current it is drawing from mains power
supply.

3. An LED is operating at 3.0 V and drawing a current of 150 mA. What is its power output?

1. In the laboratory experiment the voltage across a light bulb was taken and the current wa measured:

• Draw the circuit diagram of this experiment in the box provided. Light bulb voltage = 12 V and current + 1.5 A.

Calculate the power output of the bulb.

The bulb has a maximum rating of 12 V. If the voltage exceeded 12 V what would happen to the bulb? Explain why this is the case.