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,

the minimum amperage that the current in this wire would have to have so that its weight is completely supported by the magnetic force due to earth's field, assuming that no other forces except gravity act on it