A solar cell generates a potential difference of 0.1213 V when a 500 ohm resisto

Question

A solar cell generates a potential difference of 0.1213 V when a 500 ohm resistor is connected across it, and a potential difference of 0.1827 V when a 1000 ohm resistor is substituted. What is the internal resistance of the solar cell? Tries 0/7 What is the emf of the solar cell? Tries 0/7 The area of the cell is 5.0 cm^2, and the rate per unit area at which it receives energy from light is 2.0m W/cm^2. What is the efficiency of the cell for converting the light energy to thermal energy in the 1000 ohm external resistor? (percent = Do not enter a unit) Tries 0/7

Explanation / Answer

POtential diff across cell,

V = e - Ir

and I = e / (r + R)

V = e - ( r e / (r + R))

V = e[ 1 - (r / (r + R))]

0.1213 = e [1 - r/(500 + r)] ........ (i)

0.1827 = e [ 1 - r /(1000 + r)] ...... (ii)

(ii) / (i) => 0.1827 / 0.1213 = [ 1 - r /(1000 + r)] / [1 - r/(500 + r)]

1.506 = [ 1000 + r - r / (1000 + r)] / [ 500 / (500 + r)]

1.506 = 2 (500 + r) / (1000 + r)

1506 + 1.506r = 1000 + 2r

r = 1025 ohm ..........Ans

0.1213 = e - I r = e - (e r) /(r + R)

0.1213 = e [ 1 - (1025)/(1025 + 500)]

e = 0.37 Volt ..........Ans

Energy recieving rate = (2 m W / cm^2) (5 cm^2)

= 10 mW

in case of 1000 ohm resistor,

I = 0.1827 A

P = 0.1827^2 / 1000 = 0.033 x 10^-3 W = 0.033 mW

efficiency = (0.033 / 10 ) x 100 = 0.33 %

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