Question

Two heater coils A and B, made of the same material, are connected in parallel across mains. The length of diameter of A are double of those of B. Heat produced in

• A. A is doubled of that produced in B
• B. B is doubled of that produced in A
• C. A is four times that produced in B
• D. B is four times that produced in A

Answer 1

The correct option is A A is doubled of that produced in B

Power developed $\alpha$ Resistance and resistance of a conductor is given by;

$\begin{array}{c}R=\rho \frac{l}{A}\left(\rho -resis\tan ce\right)\left(l-lengthalongcurrentflow\right)\\ and\sin nceA\left(Area\right)\propto r^2\\ R\propto \frac{1}{r^2}\end{array}$

If the radii is doubled resistance will decrease by $4$ folds.

Hence that produced is four times that in $A$