Conservation and dissipation of energy

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Question 27
Medium

An industrial geothermal pump is labelled with its electrical power input.

a.

What is the definition of the "power input" of an electrical pump?

Select one option:

  • The rate of flow of electrical charge through the pump.
  • The total electrical energy transferred to the pump each second.
  • The average potential difference across the pump's motor.
  • The mechanical work done by the pump on the water each second.
[1]
b.

Write down the equation which links current, potential difference and power.

[1]
c.

A high-capacity coolant pump has an electrical power input of 1800 W1800 \text{ W}1800 W. The operating potential difference is 110 V110 \text{ V}110 V.

Calculate the current in the pump motor. Round your answer to 2 significant figures.

[2]
d.

Table 1 shows performance details for three geothermal pump designs.

Geothermal pumpTotal power input in wattsUseful power output in wattsEfficiency
X4003200.80
Y12009000.75
Z750WWW0.68

Write down the equation which links efficiency, total power input and useful power output.

[1]
e.

Calculate the value of WWW in Table 1.

[2]
f.

In addition to electrical power input, geothermal pumps are also labelled with their useful mechanical output power. Suggest why this is important for a system design engineer.

[2]

Conservation and dissipation of energy Questions

  1. GCSE
  2. /Physics
  3. /Conservation and dissipation of energy