Question

A 104-hp (shaft output) electric car is powered by an electric motor mounted in the engine compartment. If the motor has an average efficiency of 91 percent, determine the rate of heat supply by the motor to the engine compartment at full load.

Answer 1

Answer:

10.28571 hp

Explanation:

$W_{shaft}$ = Shaft output power = 104 hp

$\eta$ = Average efficiency = 91%

Electric work done rate is given by

$W_{el}=\dfrac{W_{shaft}}{\eta}$

The rate of heat supply is given by

$Q=W_{el}-W_{shaft}\\\Rightarrow Q=W_{shaft}(\dfrac{1}{\eta}-1)\\\Rightarrow Q=104(\dfrac{1}{0.91}-1)\\\Rightarrow Q=10.28571\ hp$

The heat supply by the motor to the engine compartment at full load is 10.28571 hp