physics

A wire of initial length L0 and radius r0 has a measured resistance of 2.5 . The wire is drawn under tensile stress to a new uniform radius of r = 0.45r0. What is the new resistance of the wire?

  1. 👍
  2. 👎
  3. 👁
  1. Rₒ=2.5 Ω (units?) , Lₒ, rₒ,
    r=0.45•rₒ.
    R =?

    The wire volume stays constant
    V= Aₒ•Lₒ = A•L => Lₒ/L =A/Aₒ.
    Rₒ=ρ•Lₒ/Aₒ,
    R=ρ•L/A,
    Rₒ/R = Lₒ•A/L•Aₒ=
    =(Lₒ/L) •(A/Aₒ)=
    =(A/Aₒ)²= (π•r²/π•rₒ²)²=
    =(0.45•rₒ/rₒ)^4=0.041.
    R=Rₒ/0.041 = 2.5/0.041=61 Ω

    1. 👍
    2. 👎

Respond to this Question

First Name

Your Response

Similar Questions

  1. Circuits, Kirchoff

    A circuit can be used to measure the resistance of a platinum resistance thermometer (PRT). AB is a uniform resistance wire of length 1.0mandCisa sliding contact on this wire. A standard resistor R is included in the circuit. The

  2. physics

    1) a wire of length 1m has a resistance of 2 ohm.obtain the resistance if specific resistance is double,diameter is double and the length is made three times of the first.

  3. Physics!! Help!!!!!

    A wire of length L and cross-sectional area A has resistance R. What will be the resistance R_stretched of the wire if it is stretched to twice its original length? Assume that the density and resistivity of the material do not

  4. Physics

    Ten identical lengths of wire are laid closely side by side. Their combined width is measured and found to be 14.2 mm. Calculate: a)the radius of a single wire b)the volume in mm cubed of a single wire if its length is 10.0 cm.

  1. physics

    Consider two copper wires with the same cross-sectional area. Wire A is twice as long as wire B. How do the resistivities and resistances of the two wires compare? CHECK ALL THAT APPLY Wire A and wire B have the same resistance.

  2. Physics

    Two wires with the same resistance have the same diameter but different lengths. If wire 1 has length L1 and wire 2 has length L2, how do L1 and L2 compare if wire 1 is made from copper and wire 2 is made from aluminum? The

  3. physics/electrical circuits

    A given wire has a resistance of 17.5 ohms. If its length is 560 m, how much length must be cut-off from the wire in order to reduce its resistance to 10 ohms?

  4. physics

    A potentiometer circuit consists of a battery of e.m.f 5v and internal resistance 10 ohms connected in series with a 30 ohms resistor and a potentiometer wire AB of length 1m and resistance 20 ohms calculate:the total resistance

  1. physics

    The filament in an incandescent light bulb is made from tungsten (resistivity 5.6 x 10-8 Ù·m). The light bulb is plugged into a 120-V outlet and draws a current of 2.36 A. If the radius of the tungsten wire is 0.00464 mm, how

  2. Physics

    A nichrome wire has a radius of 0.50 mm and a resistivity of 1.5 ´ 10‑6 W‑m. What is the resistance per unit length of this wire?

  3. science

    A wire of resistance 12 ohm per metre is bent to form a complete circle of radius 10 c.m.the resistance between its two diametrically opposite point A and B

  4. Math

    The electrical resistance of a wire waves directly as its length & inversely as the square of its diameter if a wire 30m long and 0.75mm in diameter has a resistance of 25ohms , find the length of a wire of the same material whose

You can view more similar questions or ask a new question.