A) 4
B) 10
C) 8
D) 20
Correct Answer: C
Solution :
Suppose n resistors are used for the required job. Suppose equivalent resistance of the combination is R' and according to energy conservation it's current rating is \[i'.\] Energy consumed by the combination = n ´ (Energy consumed by each resistance) Þ \[i{{'}^{2}}R'=n\times {{i}^{2}}R\]Þ \[n={{\left( \frac{i'}{i} \right)}^{2}}\times \left( \frac{R'}{R} \right)={{\left( \frac{4}{1} \right)}^{2}}\times \left( \frac{5}{10} \right)=8\]
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