Question:
In the circuit given below, each of three resistors of \(4\Omega\) can have a maximum power of \(20\,\text{W}\) otherwise, it will melt. The maximum power which the whole circuit can take is:
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In the circuit given below, each of three resistors of \(4\Omega\) can have a maximum power of \(20\,\text{W}\) otherwise, it will melt. The maximum power which the whole circuit can take is:
center
Show Hint
The resistor carrying highest current usually reaches limiting power first. Check that resistor before calculating total allowable power.
Updated On: Jun 17, 2026
- \(30\,\text{W}\)
- \(40\,\text{W}\)
- \(20\,\text{W}\)
- \(10\,\text{W}\)
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The Correct Option is A
Solution and Explanation
Two \(4\Omega\) resistors are in parallel:
\[
R_p=\frac{4\times4}{4+4}=2\Omega
\]
This combination is in series with another \(4\Omega\):
\[
R_{eq}=2+4=6\Omega
\]
Let current through series resistor be \(I\).
Power in series resistor:
\[
P=I^2R
\]
Maximum allowed:
\[
20=I^2(4)
\]
\[
I^2=5
\]
Total circuit power:
\[
P_{total}=I^2R_{eq}
\]
\[
P_{total}=5\times6
=30\,\text{W}
\]
\[
\boxed{30\,\text{W}}
\]
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