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Practice each question, then open the answer or worked solution.
What determines the rate at which energy is delivered by a current?
Electric power is the rate of consumption of electrical energy by electric appliances. Hence, the rate at which energy is delivered by a current is the power of the appliance.
An electric motor takes 5 A from a 220 V line. Determine the power of the motor and the energy consumed in 2 h.
The power of the motor can be calculated by the equation,
P = VI
Substituting the values in the above equation, we get
P = 220 V × 5 A = 1100 W
The energy consumed by the motor can be calculated using the equation,
E = P × T
Substituting the values in the above equation, we get
P = 1100 W × 7200 = 7.92 × 106 J
The power of the motor is 1100 W and the energy consumed by the motor in 2 hours is 7.92 × 106 J.