A domestic electric kettle is rated at $1500 W$ and is designed to operate on a $230 V$ supply.

hard 5 marks Class 10 · Science · Electricity

Answer

Current =

6.52 A

; Resistance =

35.3 Ω

; Energy consumed =

11.25 kWh

; Cost = Rs 78.75.

The correct answer is Current = $6.52 A$ ; Resistance = $35.3 Ω$ ; Energy consumed = $11.25 kWh$ ; Cost = Rs 78.75. — Cost = energy $\times$ rate = $11.25 kWh \times R s 7/ kWh = R s 78.75$ .

Step-by-step solution

(a) Use the power formula $P = V I$ rearranged as $I = \frac{P}{V}$ .
Substitute $P = 1500 W$ and $V = 230 V$ : $I = \frac{1500}{230} \approx 6.5217 A$ , so $I \approx 6.52 A$ .
(b) Use Ohm\'s law $R = \frac{V}{I}$ .
Substitute $V = 230 V$ and $I = 6.5217 A$ : $R = \frac{230}{6.5217} \approx 35.29 Ω$ , so $R \approx 35.3 Ω$ .
(c) Convert daily usage time to hours: $15 min = 0.25 h$ .
Power of the kettle in kilowatts: $1500 W = 1.5 kW$ .
Energy used per day: $E_{d a y} = 1.5 kW \times 0.25 h = 0.375 kWh$ .
For 30 days: $E_{m o n t h} = 0.375 \times 30 = 11.25 kWh$ .
Cost = energy $\times$ rate = $11.25 kWh \times R s 7/ kWh = R s 78.75$ .

Common mistake: Using minutes directly without converting to hours, or using

P = I^{2} R

without first finding the correct current.

Concept tested: Power, resistance and energy cost calculations

Published 24 August 2026 · How this solution was prepared and checked

A domestic electric kettle is rated at 1500 W and is designed to operate on a 230 V supply.

Step-by-step solution

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A domestic electric kettle is rated at $1500 W$ and is designed to operate on a $230 V$ supply.