Assignment 1b: (DC Circuits)
(Ohm’s Law, Power and Energy)
Problem:
1. Determine the resistance of an electric appliance which takes a current of 12 A from
A 240 V source. Find also the power rating of the appliance and energy used in 20 hr.
2. a. In 10 h an electrical system converts 500 kWh of electrical energy into heat. What
is the power level of the system?
b. If the applied voltage is 208 V, what is the current drawn from the supply?
c. If the efficiency of the system is 82%, how much energy is lost or stored in 10 h?
3. a. If a home is supplied with a 120-V, 100-A service, find the maximum power
capability.
b. Can the homeowner safely operate the following loads at the same time?
5-hp motor
3000-W clothes dryer
2400-W electric range
1000-W steam iron
4. An electric motor used in an elevator system has an efficiency of 90%. If the input
voltage is 220 V, what is the input current when the motor is delivering 15 hp?