Question

5.An electric iron is rated 220 V, 1 kW. under normal working condition, find: (1) the resistance of the heating element in the iron, (2) the amount of current that will be produced in 15 minutes . (3) if the line voltage falls to 180 V, the power consumed

Answer 1

$$\begin{gathered} weknowpowerisgivenby: \\ P=\frac{V^2}{R} \\ R=\frac{220\times 220}{1000}=48.4ohm. \\ current=\frac{V}{I}=\frac{220}{48.4}=4.5A,currentdoesnotdependontime. \\ Powerconsumedwhenconnectedto180voltsupply: \\ P=\frac{180\times 180}{48.4}=669.42Watt \end{gathered}$$