Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Current Electricity question

2017 · Q126
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /NEET
  3. /Physics
  4. /Current Electricity
  5. /2017 · Q126

Current Electricity question

2017 · Q126

NEETPhysicsCurrent ElectricityMCQ+4 / −1
The resistance of a wire is 'R' ohm. If it is melted and stretched to 'n' times its original length. its new resistance will be
  1. A
    Rn{R \over n}nR​
  2. B
    n2R
  3. C
    Rn2{R \over {{n^2}}}n2R​
  4. D
    nR
View written solutionFree

Correct answer: B

Resistance R=ρl/AR = \rho l/AR=ρl/A

l′=nll' = nll′=nl and A′=An,R′=ρlA′A' = {A \over n},R' = {{\rho l} \over {A'}}A′=nA​,R′=A′ρl​

R′=ρnlA/n=ρlAn2R' = {{\rho nl} \over {A/n}} = {{\rho l} \over A}{n^2}R′=A/nρnl​=Aρl​n2

R′=Rn2R' = R{n^2}R′=Rn2

PreviousNext

More from Current Electricity

  • A potentiometer is an accurate and versatile device to make electrical measurements of EMF because the method involves2017 · MCQ
  • A potentiometer wire is 100 cm long and a constant potential difference is maintained across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at 50 cm and 10…2016 · MCQ
  • The charge flowing through a resistance R varies with time t is Q = at − bt2, where a and b are positive constants. The total heat produced in R is2016 · MCQ
  • The potential difference (VA − VB) between the points A and B in the given figure is Includes diagram2016 · MCQ
  • A filament bulb (500 W, 100 V) is to be used in a 230 V main supply. When a resistance R is connected in series, it works perfectly and the bulb consumes 500 W. The value of R is2016 · MCQ
  • Two metal wires of identical dimensions are connected in series. If σ1 and σ2 are the conductivity of the combination is2015 · MCQ
  • A circuit contains an ammeter, a battery of 30 V and a resistance 40.8 ohm all connected in series. If the ammeter has a coil of resistance 480 ohm and a shunt of 20 ohm, the reading in the ammeter will be2015 · MCQ
  • A potentiometer wire of length L and a resistance r are connected in series with a battery of e.m.f. E0 and a resistance r1. An unknown e.m.f. E is balanced at a length l of the potentiometer wire. The e.m.f. E will be given by2015 · MCQ