Question

A hair dryer with a resistance of 9.6 ohms operates at 120 volts for 2.5 minutes. The total electrical energy used by the dryer during this time interval is

Answer 1

Answer:

$2.25\cdot 10^5 J$

Explanation:

First of all, we have to find the power used by the hair dryer, which is given by

$P=\frac{V^2}{R}$

where

V = 120 V is the voltage

$R=9.6 \Omega$ is the resistance of the hair dryer

Substituting,

$P=\frac{(120 V)^2}{9.6 \Omega}=1500 W$

Now we can find the total electrical energy used, given by

$E=Pt$

where P is the power and

t = 2.5 min = 150 s is the time

Substituting,

$E=(1500 W)(150 s)=2.25\cdot 10^5 J$