An electric source can supply a charge of 500 coulomb. If the current drawn by a device is 25 mA, find the time in which the electric source will be discharged completely.
Generated by claude-sonnet-4-6 · 2026-06-15 06:43 · grounding rag
Model Answer
Given:
Charge, Q = 500 C
Current, I = 25 mA = 25 × 10⁻³ A = 0.025 A
Formula:
$$I = \frac{Q}{t} \implies t = \frac{Q}{I}$$
Calculation:
$$t = \frac{500}{0.025} = 20000 \text{ s} = 2 \times 10^4 \text{ s}$$
The electric source will be discharged completely in 2 × 10⁴ seconds (approximately 5.56 hours).
Source: Chapter 11, Electric Current section
---
Explanation
- The key relation is I = Q/t, rearranged to t = Q/I.
- Examiners expect you to convert mA → A before substituting (25 mA = 0.025 A). Forgetting this conversion is the most common error.
- State the formula, substitute with units, and write the final answer clearly — this secures both marks (1 for formula/working, 1 for correct answer).