A solar cell generates a potential difference of 5.62 V when a 1.20 k Ohm extern

Question

A solar cell generates a potential difference of 5.62 V when a 1.20 k Ohm external resistance is connected across it, i. e., from one terminal of the cell to the other terminal of it, and a potential difference of 6.84 V when a 2.90 k Ohm external resistance is used. What is the internal resistance r_i of the solar cell? (Give your answer in the form of " abc" Ohm) 5.25 Times 10^2 (2) Ohm 7.67 Times 10^(2) Ohm 4.67 Times 5.93 Times 10^(2) Ohm 3.93 Times^(3) Ohm What is the emf epsilon (V) of the solar cell ? 9.93 V. 7.67 J 7.07 V. 5.93 J 8.08V.

Explanation / Answer

Let the emf of the solar cell be E and the output voltage be V. Thus
V = E - ir = E - V/R *r

for both cases. Numerically we get

5.62V = E - (5.62/1200)r
6.84V = E - (6.84/2900)r

We solve for E and r.

E = 8.07779, r = 524.796

So,
a) Resistance r = 524.796 or 5.25 *10^2 Ohm
b) Emf E = 8.08 V

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