Question:

The ratio of heat dissipated per second through the resistance 5 ohm and 10 ohm in the circuit given below is :
Circuit diagram

Updated On: Mar 22, 2025
  • 1:2
  • 2:1
  • 4:1
  • 1:1
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The Correct Option is B

Solution and Explanation

Given circuit:
The 5Ω 5 \, \Omega and 10Ω 10 \, \Omega resistors are connected in parallel.

Step 1: Calculating the Equivalent Resistance
The equivalent resistance Req R_{\text{eq}} of the parallel combination is given by:

1Req=15+110. \frac{1}{R_{\text{eq}}} = \frac{1}{5} + \frac{1}{10}.

Calculating:

1Req=210+110=310    Req=103Ω. \frac{1}{R_{\text{eq}}} = \frac{2}{10} + \frac{1}{10} = \frac{3}{10} \implies R_{\text{eq}} = \frac{10}{3} \, \Omega.

Step 2: Current Division in Parallel Resistors
Let i1 i_1 be the current through the 5Ω 5 \, \Omega resistor and i2 i_2 be the current through the 10Ω 10 \, \Omega resistor. By the current division rule:

i1i2=R2R1=105=2. \frac{i_1}{i_2} = \frac{R_2}{R_1} = \frac{10}{5} = 2.

Thus, i1=2i2 i_1 = 2i_2 .

Step 3: Calculating the Power Dissipated
The power dissipated P P in a resistor is given by:

P=i2R. P = i^2R.

The ratio of the power dissipated in the 5Ω 5 \, \Omega resistor to the 10Ω 10 \, \Omega resistor is:

P1P2=i12R1i22R2=(i1i2)2×R1R2. \frac{P_1}{P_2} = \frac{i_1^2R_1}{i_2^2R_2} = \left( \frac{i_1}{i_2} \right)^2 \times \frac{R_1}{R_2}.

Substituting the values:

P1P2=(2)2×510=4×12=2. \frac{P_1}{P_2} = (2)^2 \times \frac{5}{10} = 4 \times \frac{1}{2} = 2.

Therefore, the ratio of heat dissipated per second through the 5Ω 5 \, \Omega and 10Ω 10 \, \Omega resistors is 2:1 2:1 .

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