Conceptual Physics

skepticism and opposition.

Ohm’s law: potential difference

and current

ǻV = IR

ǻV = potential difference

I = current

R = resistance

Units of resistance: ohms (Ÿ),

volts/ampere

What is the resistance of this

resistor?

R = 100 Ÿ

25.4 - Interactive problem: Ohm’s law

The interactive problem on the right shows a tanning bed, an electrical appliance

through which current can flow.

Your challenge is to configure the tanning bed so that 2.4 amperes of current flow

through it. If you accomplish this goal, Joe Pasty will get a perfect tan. Anything less

and he will remain pasty. Anything more and it will be red and toasty for Joe.

In the simulation, the potential difference applied to the lamps of the tanning bed is

240 volts. (Assume that this potential difference is unchanging.)

You can control the tanning bed’s resistance using the up and down buttons in the

control panel. The resistance can vary from 10 to 200 ohms.

Use Ohm’s law to calculate the tanning bed resistance that will result in 2.4

amperes of current flowing through the device. Set the resistance to the nearest 10

ohms, then press GO to see if you were correct. A gauge located on the tanning

bed will display the amount of current flowing through the device.

(^460) Copyright 2000-2007 Kinetic Books Co. Chapter 25