Electrical Power

Which one of the following quantities is equivalent to 1 W?

• 1 V/A

• 1 Ω • m

• 1 V • A

• 1 V/Ω

What potential difference is required across an 8.0-Ω resistor to cause 2.0 A to flow through it?

• 4.0 V

• 16 V

• 8.0 V

• 32 V

A 4000-Ω resistor is connected across a 220-V power source. What current will flow through the resistor?

• 0.055 A

• 1.8 A

• 5.5 A

• 18 A

A resistor operated at 140 V dc is rated at 1.40 kW.

(a) What is the normal operating current through the resistor?

(b) What is the resistance of the resistor?

• (a) 10 A . (b) 14 Ω

• (a) 14 A . (b) 14 Ω

• (a) 10 A . (b) 10 Ω

• (a) 0.010 A . (b) 14000 Ω

An instrument is rated at 240 W if it is connected across a 120-V dc power supply.

(a) What current does it draw under normal operation?

(b) What is its resistance?

• (a) 0.20 A (b) 360 Ω

• (a) 60 A (b) 2.0 Ω

• (a) 2.0 A (b) 60 Ω

• (a) 0.2 A (b) 60 Ω

A 200-W light bulb is connected across a 100-V dc power supply. What current will flow through this bulb?

• 0.90 A

• 0.36 A

• 0.60 A

• 2.0 A

A 100-W light bulb is operated by a 110-V dc source. What is the resistance of this bulb?

• 100 Ω

• 8.0 × 10^-3 Ω

• 120 Ω

• 240 Ω

A light bulb operating at a dc voltage of 100 V has a resistance of 200 Ω. How much power is dissipated in this bulb?

• 100 W

• 60 W

• 50 W

• 200 W

When 5.00 A is flowing through an 10.0-Ω device, how much power is being dissipated in the device?

• 50.0 W

• 250 W

• 500 W

• 2.50 kW

What is the resistance of a 0.100-kW light bulb designed to be used in a 120-V circuit dc?

• 12.0 Ω

• 144 Ω

• 1.2 Ω

• 0.83 Ω