Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
NEET 2023
Exam
NEET
Year
2023
Subject
Physics
Chapter
Current Electricity

NEET 2023 · Physics · Current Electricity

A certain wire A has resistance 81 . The resistance of another wire...

A certain wire AA has resistance 81Ω81 \Omega. The resistance of another wire BB of same material and equal length but of diameter thrice the diameter of AA will be

Options

  1. A729Ω729 \Omega
  2. B243Ω243 \Omega
  3. C81Ω81 \Omega
  4. D9Ω9 \Omega

Correct answer

D. 9Ω9 \Omega

Step-by-step solution

We know that, R=ρlAR=\frac{\rho l}{A}, where A=π4d2A=\frac{\pi}{4} d^2⇒81=ρ×Iπ4d2, also, R′=ρ×Iπ4×(3d)2=ρlπ4×9d2⇒R′=R9=819=9Ω\begin{aligned} & \Rightarrow 81=\frac{\rho \times I}{\frac{\pi}{4} d^2}, \text{ also, } R^{\prime}=\frac{\rho \times I}{\frac{\pi}{4} \times(3 d)^2}=\frac{\rho l}{\frac{\pi}{4} \times 9 d^2} \\ & \Rightarrow R^{\prime}=\frac{R}{9}=\frac{81}{9}=9 \Omega\end{aligned}$$
Practice Current Electricity on Quantrex Academy →

More from Current Electricity

A potentiometer wire of 400\ cm length has a resistance of 20\ Ω . It is connected in… MHT CET Medical 2026In the following figure current I equal to MHT CET Medical 2026The range of voltmeter is 10\ V and its resistance is 50\ Ω . To convert it to a… MHT CET Medical 2026When a galvanometer is shunted with a 2\ Ω resistance, the deflection is reduced to… MHT CET Medical 2026A galvanometer can be converted into a voltmeter of certain range by connecting a… MHT CET Medical 2026A resistance is to be measured using a meter bridge; the student chooses the standard… MHT CET Medical 2026Which of the following statements is FALSE? A. In a balanced Wheatstone bridge, if the… MHT CET Medical 2026A potentiometer wire has length 4 m and resistance 8\ Ω . The resistance that must be… MHT CET Medical 2026 Full Current Electricity list All NEET PYQs