Calculating DC Power
Power is the rate at which electrical energy is used. It is measured in watts The formula for DC power consumed by a circuit is:
Power is equal to the voltage across the circuit, E, times the current flowing through the circuit.
This equation can also be rearranged to find the current in a circuit if you know the power and the voltage:
Exam Questions
Electrical power is measured in which of the following units?
A. Volts
B. Watts
C. Ohms
D. Amperes
Which term describes the rate at which electrical energy is used?
A. Resistance
B. Current
C. Power
D. Voltage
What is the formula used to calculate electrical power in a DC circuit?
A. Power (P) equals voltage (E) multiplied by current (I)
B. Power (P) equals voltage (E) divided by current (I)
C. Power (P) equals voltage (E) minus current (I)
D. Power (P) equals voltage (E) plus current (I)
How much power is being used in a circuit when the applied voltage is 13.8 volts DC
and the current is 10 amperes?
A. 138 watts
B. 0.7 watts
C. 23.8 watts
D. 3.8 watts
How much power is being used in a circuit when the applied voltage is 12 volts DC and
the current is 2.5 amperes?
A. 4.8 watts
B. 30 watts
C. 14.5 watts
D. 0.208 watts
How many amperes are flowing in a circuit when the applied voltage is 12 volts DC and
the load is 120 watts?
A. 0.1 amperes
B. 10 amperes
C. 12 amperes
D. 132 amperes