Electrical Circuit Theory and Technology 6th Edition by John Bird

Question

Electrical Circuit Theory and Technology 6th Edition by John Bird

Edition 6ISBN: 978-1138673496

Electrical Circuit Theory and Technology 6th Edition by John Bird

Edition 6ISBN: 978-1138673496

Exercise 2

A d.c. motor consumes 47.25 MJ when connected to a 250 V supply for 1 hour 45 minutes. Determine the power rating of the motor and the current taken from the supply.

Explanation

Verified

\text { Power }=\frac{\text { energy }}{\text { time }}=\frac{47.25 \times 10^{6} \mathrm{~J}}{105 \times 60 \mathrm{~s}}=7500 \mathrm{~W}

\text { i.e. power rating of motor is } 7.5 \mathrm{~kW}

\text { Power } \mathrm{P}=\mathrm{VI} \text { from which, current } \mathrm{I}=\frac{\mathrm{P}}{\mathrm{V}}=\frac{7500}{250}=30 \mathrm{~A}

\text { i.e. the current taken from the supply is } 30 \mathrm{~A}