Question

Your 60-watt light bulb is plugged into a 110-volt household outlet and left on for 3 hours. Of each kWh costs $0.11, about how much money does the energy company charge you?

Answer 1

Answer: A. The current in a 60-Watt bulb plugged into a 120-Volt outlet is 0.5 A.  

I = P / V = (60 W) / (120 V) = 0.5 A

For each problem, use the P = V • I equation to solve for the unknown quantity. In a, b, and e, the unknown quantity is current (I); and in c and d, the unknown quantity is power (P).

Other answers:

b. The current in a 120-Watt bulb plugged into a 120-Volt outlet is 1.0 A.

I = P / V = (120 W) / (120 V) = 1.0 A  

c. The power of a saw that draws 12 amps of current when plugged into a 120-Volt outlet is 1440 W.

P = V • I = (120 V) • (12 A) = 1440 W

d. The power of a toaster that draws 6 amps of current when plugged into a 120-Volt outlet is 720 W.

P = V • I = (120 V) • (6 A) = 720 W

e. The current in a 1000-Watt microwave when plugged into a 120-Volt outlet is 8.3 A.

I = P / V = (1000 W) / (120 V) = 8.3 A