Page 46 - Basic Electrical Engineering
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= 30 min = 30 × 60 s
=1800 secs.
The power rating of the heater
Current drawn from 230 V supply
P = VI = 870 Watts.
Therefore,
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Example 1.4 A motor-driven water pump lifts 64 m of water per minute to
an overhead tank placed at a height of 20 metres. Calculate the power of the
pump motor. Assume overall efficiency of the pump as 80 per cent.
Solution:
Work done/min = mgh Joules
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m = 64 × 10 kg (1m of water weights 1000 kg)
g = 9.81 m/sec 2
h = 20 m
Substituting values
Work done/sec
