Electrical Power Calculations

The voltage drop in a cable carrying 10.5 amperes is 4.6 volts. Calculate the power wasted in the cable.

• 49.2 watts

• 48.6 watts

• 48.9 watts

• 48.3 watts

A d.c. machine takes 18.6 amperes from a 220-volt supply. Calculate the machine’s input power.

• 4092 watts

• 4080 watts

• 4100 watts

• 4075 watts

Calculate the voltage drop in a resistor, when the power absorbed is 9kW and the current flowing is 63 amperes.

• 160 V

• 150 V

• 142.86 V

• 170 V

An appliance is rated at 3kW 240 volts. Calculate the current drawn from the supply.

• 10 A

• 12.5 A

• 15 A

• 20 A

Two resistors of 25Ω and 95Ω are connected in series across a 240 volt dc supply. What is the total power drawn from the supply?

• 480 W

• 600 W

• 720 W

• 960 W

What is the value of the resistor that absorbs 1kW of power when a current of 10 amperes is flowing?

• 1 ohms

• 100 ohms

• 10 ohms

• 0.1 ohms

A joint in a cable has a resistance of 0.0236Ω. Calculate the power developed in the joint when a current of 40 amperes is flowing in the cable.

• 37.76 W

• 38.24 W

• 37.44 W

• 36.96 W

Determine what the rating of a 2kΩ resistor should be in watts, if it has to be capable of carrying a current of 30mA.

• 0.9 watts

• 1.8 watts

• 0.45 watts

• 0.6 watts

Calculate the power loss in a cable of 0.25Ω when a current of 30 amperes is flowing.

• 112.5 watts

• 400 watts

• 225 watts

• 900 watts

Three resistors of 1Ω, 0.005kΩ and 500mΩ are connected in series across a 52 volt d.c. supply. What is the total power supplied to the circuit?

• 512 W

• 416 W

• 226 W

• 113 W