A solar cell generates a potential difference of 0.1123 V when a 500 resistor is

Question

A solar cell generates a potential difference of 0.1123 V when a 500 resistor is connected across it, and a potential difference of 0.1662 V when a 1000 resistor is substituted.
What is the internal resistance of the solar cell? What is the solar cell's emf? The area of the cell is 5.0 cm2, and the rate per unit area at which it receives energy from light is 2.0m W/ cm2. What is the efficiency of the cell for converting the light energy to thermal energy in the 1000 external resistor? (use percent)

Explanation / Answer

V1 = initial potential difference = 0.1123              , R1 = 500

V2 = final potential difference = 0.1123              , R2 = 1000

Using the equation

r = (E - V)R / V

so (E - V1)R1 / V1 = (E - V2)R2 / V2

(E - 0.1123) (500) / (0.1123) = (E - 0.1662) (1000) / (0.1662)

E = 0.3196

r = (E - V1)R1 / V1 = (0.3196 - 0.1123) (500) / (0.1123)

r = 922.975

Pin = Power input = Area x 2 mW/cm^2 = 5 x 2 = 10 x 10-3 Watt

Pout = power output in 1000 ohm = V2 / R = 0.16622 / 1000 = 0.02762 x 10-3 watt

Efficiency = 0.02762 x 10-3 / 10 x 10-3 = 0.002762 = 0.2762 %

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