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Math Help - Internal Resistance and Solar Cells

  1. #1
    Super Member Aryth's Avatar
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    Internal Resistance and Solar Cells

    A solar cell generates a potential difference of 0.10 V when a 500 \Omega resistor is connected across it, and a potential difference of 0.15 V when a 1000 \Omega is substituted. What are the (a) internal resistance and (b)emf of the solar cell? (c) The area of the cell is 5.0 cm^2, and the rate per unit area at which it receives energy from light is 2.0 \frac{mW}{cm^2}. What is the efficiency of the cell for converting light energy to thermal energy in the 1000 \Omega external resistor?
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    Senior Member vincisonfire's Avatar
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    a) b) \epsilon - R_{int}I = V
     \epsilon = (R_{int}+R_{ext})I
     \epsilon = V+RI = V+R\frac{\epsilon}{R_{int}+R_{ext}}
     V= R_{ext}\frac{\epsilon}{R_{int}+R_{ext}}
    Solve for R and then for  \epsilon
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    Senior Member vincisonfire's Avatar
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    c)  P_i = 5 \cdot 2 = 10 \frac{mW}{cell}
     I = \frac{\epsilon-V}{R_{int}}
     P_f = IR_{ext}^2
     \% = \frac{P_f}{P_i}
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    Super Member Aryth's Avatar
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    Thanks. I appreciate the help. There are some problems out of my league.
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