WAEC - Physics (2023 - No. 33)
A cell of emf 2 V has an internal resistance of 0.5 Ω. A current of 0.4 A passes through an external resistor, P. Determine the resistance of P.
4.5Ω
5Ω
1Ω
4Ω
Explanation
E = 2V, r = 0.5Ω, I = 0.4A, P = ?
E = I( R + r )
R = \(\frac{ E}{I} - r \)
R = \(\frac{ 2}{0.4} - 0.5\)
R = 5 - 0.5 = 4.5Ω
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