Question

A calculator runs on a solar cell with an area of $1.0 \times {10}^{-3}{m}^{2}$. When it is illuminated by a light of intensity of $1.0 \times {10}^{2} {Wb}/{{m}^{2}}$ it produces an EMF of 0.60V and produces a current of 0.0030A to power the calculator. What is the efficiency of solar cells?

Answer 1

Hint: This problem can be solved using the formula for efficiency. Initially, we have to calculate the output power. So, use the relation between voltage, power and current to find the output power. Then, use the formula for efficiency. Substitute the values of output power, incident radiation and area. Multiply this value by 100 to get the efficiency in percentage. This obtained value is the efficiency of solar cells.

Formula used:
$P= VI$
$\eta= \dfrac {P}{E \times A} \times 100\%$

Complete answer:
Given: EMF (V) = 0.6V
             Current (I) =0.0030A
             Area (A)= $1.0 \times {10}^{-3}{m}^{2}$
             Incident radiation (E)= $1.0 \times {10}^{2} {Wb}/{{m}^{2}}$
Relation between power, current and voltage is given by,
$P= VI$
Substituting the values in above equation we get,
$P= 0.6 \times 0.0030$
$\Rightarrow P= 0.0018 W$
Formula for efficiency is given by,
$\eta= \dfrac {P}{E \times A} \times 100\%$
Substituting the values in above equation we get,
$\eta= \dfrac {0.0018}{1.0 \times {10}^{2} \times 1.0 \times {10}^{-3} } \times 100\%$
$\Rightarrow \eta = 0.0018 \times {10}^{-1} \times 100\%$
$\Rightarrow \eta = 0.018 \times 100\%$
$\Rightarrow \eta= 1.8\%$
Hence, the efficiency of solar cells is 1.8%.

Note:
As efficiency is in percentage, so keep in mind to multiply the efficiency by 100%. Solar cell is a device used to convert solar energy to electric energy. It is based on the principles of photovoltaic effect. Unlike batteries, solar cells do not use chemical reactions to produce electric power. And unlike generators, it does not have any moving part. Majority of solar cells are formed from silicon. It produces low current but this current is sufficient enough to display the output.