Question

1. An electric iron is rated at 230 V, 750 W. Calculate
   1. the maximum current, and
   2. the number of units of electricity it would use in 30 minutes.
2. Which of the following fuse ratings would be suitable for this electric iron?
   1 A, 3 A, 5 A, 13 A

Answer 1

a. Given: V = 230 V

P = 750 W

T =  30 min = 0.5 hours

i. Let the maximum current be I.

We know that,

P = VI

⇒ 750 = 230 I

⇒ I = `750/230`

⇒ I = 3.26 A

ii. Electric energy consumed,

E = PT

⇒ E = 0.75 kW × 0.5 hours

⇒ E = 0.375 kWh

∴ The number of units used in 30 minutes is 0.375.

b. The maximum current for the given iron is 3.26 A; therefore, a 5 A fuse rating will be suitable for the electric iron.