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If the electromotive force (emf) is 2.1 V, the current is 0.2 A, and the external resistance is 10 Ω, what is the internal resistance of the circuit?

1. Using the equation, emf = I(r + R)
2. 2.1 - 0.2r = 0.2 × 10
3. 2.1 - 0.2r = 2
4. r = 0.1 ÷ 0.2 = 0.5 Ω

Correct answer: r = 0.1 ÷ 0.2 = 0.5 Ω

Solution

Using the formula E = Ir + IR, substituting the given values, we solve for r: 2.1 = 0.2r + (0.2 × 10). Simplifying, 2.1 - 2 = 0.2r, so r = 0.1 / 0.2 = 0.5 Ω.

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