Current Electricity

JEE Main level, single correct, medium

65 of 380

Question 65 of 380

Given below are two statements :
Statement I : A uniform wire of resistance
80Ω80\Omega is cut into four equal parts. These parts are now connected in parallel. The equivalent resistance of the combination will be 5Ω5\Omega.
Statement II : Two resistance
2R2R and 3R3R are connected in parallel in an electric circuit. The value of thermal energy developed in 3R3R and 2R2R will be in the ratio 3:23:2.
In the light of the above statements, choose the most appropriate answer from the options given below

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Answer: (C) Statement I is correct but statement II is incorrect

Statement 1−1- R=80ΩR=80\Omega
When it is cut into
44 equal parts, the resistance of each part will be,
R1=R2=R3=R4=20Ω{R}_{1}={R}_{2}={R}_{3}={R}_{4}=20\Omega
When these resistances are connected in parallel,

Req=204=5Ω{R}_{eq}=\dfrac{20}{4}=5\Omega
Hence, the statement I is correct.

Statement 2 -


When the resistances are connected in parallel, the potential difference between them is same. Therefore, the power consumed can be written as,

P=V2RP=\dfrac{{V}^{2}}{R}
⇒P1P2=(R2R1)=23\Rightarrow \dfrac{{P}_{1}}{{P}_{2}}=\left(\dfrac{{R}_{2}}{{R}_{1}}\right)=\dfrac{2}{3}
Hence, statement II is incorrect.

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