A solar cell generates a potential difference of 0.10 V when a 500 resistor is c

Question

A solar cell generates a potential difference of 0.10 V when a 500 resistor is connected across it, and a potential difference of 0.15 V when a 1000 resistor is substituted.
(a) What is the internal resistance of the solar cell?
_____ohms

(b) What is the emf of the solar cell?
_____V

(c) The area of the cell is 2.0 cm2, and the rate per unit area at which it receives energy from light is 2.0 mW/cm2. What is the efficiency of the cell for converting the light energy to thermal energy in the 1000 external resistor?
_____%

Explanation / Answer

consider the emf of solar cell be and the output voltage be V . thus                      V = - i r                           = - ( V / R ) r     potential difference of 0.10 V when a 500 resistor is connected across the solar cell                    0.1 V =   - ( 0.1 V / 500 ) r .......(1)         potential difference of 0.15 V when a 1000 resistor is connected across the solar cell                                           0.15 V = - ( 0.15 V / 1000 ) r ..........(2)     on solveing equations (1) and (2)     a)        internal resistance        r = 1000     b)        emf of the solarcell is =  0.3 V        c) received energy from light is   P received = 2.0 mW/cm2                                                                         = (  2.0 mW/cm2   ) ( 2 cm 2 )                                                                        = 4 mW         efficiency of the cell for converting the light energy to thermal energy in the 1000 external resistor                            =   ( 0.15)2 / 1000 * 4*10-3 W                               = 5.625*10-3                            = 0.562 %                                                                       = (  2.0 mW/cm2   ) ( 2 cm 2 )                                                                        = 4 mW         efficiency of the cell for converting the light energy to thermal energy in the 1000 external resistor                            =   ( 0.15)2 / 1000 * 4*10-3 W                               = 5.625*10-3                            = 0.562 %       

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