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Heat Generated Electrical Energy • Electrical energy is the energy delivered over a period of time • Energy (in joules) generated =P(Watts) x t(sec) • Energy (in kW-h) generated =P(kW) x t(hr) Sample Problem 1. An electric motor takes 5 A from a 110 V line. Determine the power input and the energy in J and kW – h, supplied to the motor in 2 h. Seatwork 1. An electric iron of resistance 20 ohms takes a current of 5 A. Calculate the heat in Joules developed in 30 seconds. 2. An electric heater of resistance 8 ohms draws 15 A from the service mains. At what rate is heat developed in watts? What is the cost of operating the heater for a period of 4 h at P4.90/ kW – h