Ahair 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

Explanation:

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

where

V = 120 V is the voltage

is the resistance of the hair dryer

Substituting,

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

where P is the power and

t = 2.5 min = 150 s is the time

Substituting,

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .