Question

An electric kettle has three thermal coils A, B and C. To boil the same amount of water coil A, B and C take 2 min, 3 min and 6 min respectively when applied across same potential difference. If all three coils are operated together and same potential difference is applied across the combination, then to boil same amount of water​

Answer 1

Answer:

36/11 0r 3.27

Explanation:

Q= $\frac{V^2}{R1}$   ×t1        

Q=$\frac{V^2}{R2}$    ×t2

Q=$\frac{v^2}{R3}$     ×t3

$\frac{1}{R}$=$\frac{1}{R1} + \frac{1}{R2} +\frac{1}{R3}$

$\frac{Q}{V^2t} =\frac{Q}{V^2t1} +\frac{Q}{V^2t2} +\frac{Q}{V^2t3}$

$\frac{1}{t} =\frac{1}{t1} +\frac{1}{t2}+\frac{1}{t3}$

t=$\frac{t1t2t3}{t1+t2+t3}$

t=$\frac{2.3.6}{2+3+6} = \frac{36}{11}$

t=3.27min