A solar cell generates a potential difference of 0.1519 V when a 500 resistor is

Question

A solar cell generates a potential difference of 0.1519 V when a 500 resistor is connected across it, and a potential difference of 0.2216 V when a 1000 resistor is substituted. A.What is the internal resistance of the solar cell?

B. What is the emf of the solar cell?

C. 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 light energy to thermal energy in the 1000 external resistor? (Give answer in %. Do not enter unit)

Explanation / Answer

Part A:

E = emf
r = internal resistance
E - I*r = V
E - (0.1519/500)*r = 0.1519
E - (0.2216/1000)*r = 0.2216
so, (-3.038*10^-4 + 2.216*10^-4)*r = 0.1519 - 0.2216

r = -0.0697 /-0.822*10^-4

the internal resistance of the solar cell, r = 847.9

Part B:

E = 0.2216 + (-3.038*10^-4 )*847.9 V = 0.2216 - 0.2576

emf of the solar cell = - 36 mV

Part C:
P dissipated Po = V^2 / R = 0.2216^2 / 1000 = 4.91*10^-5 W

P received Pi = 2.0*10^-3 V/cm^2 * 5 cm^2 = 1.0*10^-2 W

Efficiency = Po/Pi = 0.0049 = 0.49 %

the efficiency of the cell for converting light energy to thermal energy in the 1000 external resistor is 0.49%

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