Physics Chapter 34 - Calculating Power Practice

Valerie's 180 W electric rollers are plugged into a 120 V line in her bedroom. a) What current do the electric rollers draw? b) What is the resistance of the rollers when they are heated?

Answer A: I = P/V I = (180)/(120) I = 1.5 A Answer B: R = V/I R = (120)/(1.5) R = 80 Ohms

How much power is used by a set of lights operating on a 12 V battery and 2.75 A?

P = (12)(2.75) P = 33 W

An 8.0 V power supply delivers a 1.75 A current to a circuit. Calculate the power provided to the circuit.

P = (8.0)(1.75) P = 14 W

What is the equation you use to calculate power?

P = VI

How much power is used by an ultrasonic jewelry cleaner that draws 0.042 A of current from a 120 V line?

P = VI P = (0.042)(120) P = 5.0 W

A 15 W motor draws a current of 1.25 A. What is the voltage impressed across the circuit?

V = (15)/(1.25) V = 12 V