A toaster is plugged into an 120-volt outlet. If it has a resistance of 460 ohms, how much power does it use?

A. 1,800 watts

B. 3.8 watts

C. 31 watts

D. 55,000 watts

E. 340 watts

Here are a few formulas for electrical power:

P = (voltage) x (current)

P = (voltage) ² / (resistance)

P = (current) ² x (resistance)

We know the voltage and the resistance, so it seems to me that

we should use the middle one.

Power = (voltage) ² / (resistance)

= (120 volts) ² / (460 ohms)

= (14,400 volts²) / (460 ohms)

= 31.3 watts.

That's not much power for a toaster. It produces about as much heat

as a small (30 watt) light bulb.

You would not sell many toasters designed like this one, because

it would take several days to toast a slice of bread.

A toaster that has what it takes to do the job will typically use

1200 watts to 1600 watts, just like a typical blow-dryer.