An electric motor rated 1100 W is connected to 220 V mains. Find : (i) The current drawn from the mains, (ii) Electric energy consumed if the motor is used for 5 hours daily for 6 days. (iii) Total cost of energy consumed if the rate of one unit is ₹ 5.
Generated by claude-sonnet-4-6 · 2026-06-15 06:47 · grounding rag
Model Answer
Given: P = 1100 W, V = 220 V, time = 5 h/day for 6 days
(i) Current drawn from mains:
Using P = VI,
$$I = \frac{P}{V} = \frac{1100 \text{ W}}{220 \text{ V}} = 5 \text{ A}$$
(ii) Energy consumed:
Total time = 5 × 6 = 30 hours
$$\text{Energy} = P \times t = 1100 \text{ W} \times 30 \text{ h} = 33000 \text{ Wh} = 33 \text{ kWh}$$
(iii) Total cost:
$$\text{Cost} = 33 \text{ units} \times ₹5 = ₹165$$
Source: Chapter 11, Section 11.8 Electric Power
---
Explanation
- Examiners expect the formula to be stated, values substituted, and units written clearly for each part.
- 1 kWh = 1 unit; always convert Wh → kWh before calculating cost.
- Budget: ~1 mark per sub-part — keep each part to 2–3 lines.