A battery of emf 12.0 V and internal resistance of 1.0 Ω is connected to an external resistor 3.0 Ω.

JAMB Physics 2023 176 views
Source: JAMB · 2023

A battery of emf 12.0 V and internal resistance of 1.0 Ω is connected to an external resistor 3.0 Ω. Find the power delivered by the battery.

  1. 18 W
  2. 36 W ✓
  3. 27 W
  4. 15 W
Explanation

Calculate current first: I = EMF/(R + r) = 12/(3 + 1) = 3 amperes. Total resistance includes both internal and external resistance.

Power delivered by battery equals EMF times current: P = EMF × I = 12 × 3 = 36 watts.

This is total power from the battery. Some power dissipates in internal resistance, and the rest goes to the external resistor.

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