Question

(a) An electric iron is rated at 230 V, 750 W. Calculate (i) the maximum current, and (ii) the number of units of electricity it would use in 30 minutes.

(b) Which of the following fuse ratings would be suitable for electric iron ?

1 A, 3 A, 5 A, 13 A

Answer 1

(a) Voltage ( V )=230V,

Power (P ) =750 W,

tiime ( t ) = $\frac{30}{60}$ =0.5hr

(i) Let max current be
We have P=VI
750 =230 x I
I= 3.26 A
(ii) Electric energy consumed, E = (P )x ( t) = 0.75kW x 0.5h = 0.375 kWh
No. of units used in 30 min = 0.375
(b) 5 A fuse rating will be suitable for this electric iron as the maximum current for this iron is 3.26 A.