Solar cell and Resister connection A solar cell generates a potential difference

Question

Solar cell and Resister connection

A solar cell generates a potential difference of 0.260 V when a 380.0 resistor is connected across it and a potential difference of 0.434 V when a 880.0 resistor is substituted.

What is the internal resistance of the cell in Ohms?
What is the emf of the cell?
The area of the cell is 25.0 cm2 and the rate per unit area at which it receives light energy is 50.0 mW/ cm2. What is the efficiency of the cell for converting light energy to thermal energy in the 880.0 external resistor?

Explanation / Answer

here by using the formula

e = emf

V = e - I * r

then put the values in the equation

0.26 = e - (0.26 / 380) * r ...............(here I = V / R)...............(1)

then the second equation is

0.434 = e - (0.434 / 880) * r ....................(2)

then by subtracting both equation we get

(( - 0.434 /880 ) + ( 0.26 /380)) * r = 0.434 - 0.26

then by solving this equation we get r

r = 910.8 ohm

put the value of r in any of the two equation

0.26 = e - (0.26 / 380) * 910.8

e = 0.883V

then by using the formula

the efficiency is = V^2 / R*Preceived

= 0.434^2 / (880 * 50 * 10^-3 * 25)

= 1.7 * 10^-4 = 0.017 %

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