JEE MainPhysicsCurrent ElectricityMCQ+4 / −1
A wire when connected to mains supply has power dissipation Now the wire is cut into two equal pieces which are connected in parallel to the same supply. Power dissipation in this case is Then is
- A
- B
- C
- D
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Correct answer: B
- Initial power dissipation
Let the resistance of the original wire be .
When connected across a potential difference , the power dissipated is
- Resistance after cutting the wire into two equal pieces
Resistance is proportional to length, so when the wire is cut into two equal parts, each piece has resistance
- Equivalent resistance of two equal pieces in parallel
Each piece has resistance , and they are connected in parallel:
(Equivalently, for two equal resistors in parallel, .)
- New power dissipation
With the same supply voltage , the new power is
So,
Therefore,
Hence,
- Option check
- A: ❌
- B: ✅
- C: ❌
- D: ❌
So the correct option is B.
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