Consider an electric motor with a shaft power output of 22.5 kW and an efficiency of 85%. Determine the rate at which the motor dissipates heat to the room it is in when the motor operates at full load. In winter, this room is normally heated by a 2.5 kW resistance heater. Determine if it is necessary to turn the heater on when the motor runs at full load.

Question

Physics

Andre Klein

16 October, 15:28

Consider an electric motor with a shaft power output of 22.5 kW and an efficiency of 85%. Determine the rate at which the motor dissipates heat to the room it is in when the motor operates at full load. In winter, this room is normally heated by a 2.5 kW resistance heater. Determine if it is necessary to turn the heater on when the motor runs at full load.

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Answers (1)

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Gillian Castaneda · Answer 1

Rate of heat dissipation = 3.375 Kw

Explanation:

Given:

Old power output (Heat) = 22.5 Kw

Efficiency = 85% = 0.85

New power output (Heat) = 2.5 Kw

Find:

Rate of heat dissipation = ?

Computation:

Rate of heat dissipation = Total output power (1 - Efficiency)

Rate of heat dissipation = 22.5 Kw (1 - 0.85)

Rate of heat dissipation = 3.375 Kw

So, room heating if heat required is 2.5 Kw then,

It will not be necessary to turn the heater on.

Rate of heat dissipation by electric motor is greater than rate of heat dissipation by heater.