To calculate the heat produced by a hair dryer that is used for 5 minutes with 65% energy efficiency, we need to understand the concept of energy and power. The energy used by an electrical appliance is the product of its power and the time it is used for, while the heat produced is related to the energy used.

First, we need to calculate the power used by the hair dryer. From the context, we know that the hair dryer has a voltage of 220 V and a current of 1.4 A. Using the formula P = VI, we can calculate the power as follows:

P = 220 V × 1.4 A = 308 W

Next, we need to calculate the energy used by the hair dryer. Energy is the product of power and time, so we can calculate the energy used by the hair dryer as follows:

E = P × t

where P is the power in watts and t is the time in seconds. Since the hair dryer is used for 5 minutes, we need to convert this to seconds by multiplying by 60:

t = 5 min × 60 s/min = 300 s

Substituting the values for P and t, we get:

E = 308 W × 300 s = 92,400 J

Since the energy efficiency of the hair dryer is 65%, only 65% of the energy used is converted into useful work, while the remaining 35% is lost as heat. Therefore, the heat produced by the hair dryer is:

Q = 0.35 × 92,400 J = 32,340 J

Therefore, the heat produced by the hair dryer is 32,340 J.