(D) Let the heat required to boil the water be $H$. The power of the first coil is $P_1 = H/t_1 = H/6$ and the power of the second coil is $P_2 = H/t_

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(D) Let the heat required to boil the water be $H$. The power of the first coil is $P_1 = H/t_1 = H/6$ and the power of the second coil is $P_2 = H/t_2 = H/3$.When connected in series,the total resistance $R_s = R_1 + R_2$. Since $P = V^2/R$,we have $R = V^2/P$. Thus,$V^2/P_s = V^2/P_1 + V^2/P_2$,which simplifies to $1/P_s = 1/P_1 + 1/P_2$.Substituting $P = H/t$,we get $t_s/H = t_1/H + t_2/H$.Therefore,$t_s = t_1 + t_2 = 6 + 3 = 9\,min$.

Class 12 Physics Current Electricity Equivalent Resistance - Series and Parallel , Circuit

Medium

An electric kettle has two coils. When one of these is switched on,the water in the kettle boils in $6\,min$. When the other coil is switched on,the water boils in $3\,min$. If the two coils are connected in series,the time taken to boil the water in the kettle is ............. $min$.

A
$3$
B
$6$
C
$2$
D
$9$

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Current Electricity

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Equivalent Resistance - Series and Parallel , Circuit

In the given circuit,find the value of $V$. (in $V$)

Medium

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Three resistances of $4\,\Omega$ each are connected in the form of an equilateral triangle. The effective resistance between any two corners is:

MediumAIPMT 1993

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$A$ piece of wire of resistance $4\,\Omega$ is bent through $180^o$ at its mid-point and the two halves are twisted together. The new resistance is ............ $\Omega$.

Easy

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The equivalent resistance across points $A$ and $B$ in the circuit shown below is:

EasyWBJEE 2011

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If $400\; \Omega$ of resistance is made by adding four $100\; \Omega$ resistors of tolerance $5\%$ each,then the tolerance of the combination is .....$\%$

MediumAIEEE 2011

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An electric kettle has two coils. When one of these is switched on,the water in the kettle boils in $6\,min$. When the other coil is switched on,the water boils in $3\,min$. If the two coils are connected in series,the time taken to boil the water in the kettle is ............. $min$.

Similar Questions

In the given circuit,find the value of $V$. (in $V$)

Three resistances of $4\,\Omega$ each are connected in the form of an equilateral triangle. The effective resistance between any two corners is:

$A$ piece of wire of resistance $4\,\Omega$ is bent through $180^o$ at its mid-point and the two halves are twisted together. The new resistance is ............ $\Omega$.

The equivalent resistance across points $A$ and $B$ in the circuit shown below is:

If $400\; \Omega$ of resistance is made by adding four $100\; \Omega$ resistors of tolerance $5\%$ each,then the tolerance of the combination is .....$\%$

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