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Two conducting wires X and Y of same dia...

Two conducting wires X and Y of same diameter but different materials are joined in series across a battery. If the number density of electrons in X is twice that in Y, find the ratio of drift velocity of electrons in the two wires.

Text Solution

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Here current, l, is same in both wires. Moreover `I prop n v_d`. `thereforev_(dx)/v_dy=n_y/n_x=1/2`
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Knowledge Check

  • If a current passes through a metal conducting wire of area of cross section A, the drift velocity of free electrons inside the metal is v_d=1/( n e A) , where the amount of electric charge of an electron =e and the number of free electrons per unit volume of the metal=n. The applied electric field on the wire is E=V/l , where a potential difference V exists between two points, l apart, along the length of the wire. IF R is the resistance of the wire between those two points, then the resistivity of its material is rho=(RA)/l .Besides the mobility (mu) of the free electrons inside a wire is defined as their drift velocity for a unit applied electric field. The radii of two wires ,made of two different metals are in the ratio 1:2 , The number density of free electrons in the first metal is double that in the second metal. IF the current in the first wire is 1A, then the current in the second wire producing the same drift velocity is

    A
    1A
    B
    2A
    C
    4A
    D
    8A

  • Two copper wires have a ratio of 1:4 between their diameters. IF the same current passes through both of them, the drift velocity of the electrons will be in the ratio of

    A
    `16:1`
    B
    `4:1`
    C
    `1:4`
    D
    `1:16`

  • If a current passes through a metal conducting wire of area of cross section A, the drift velocity of free electrons inside the metal is v_d=1/( n e A) , where the amount of electric charge of an electron =e and the number of free electrons per unit volume of the metal=n. The applied electric field on the wire is E=V/l , where a potential difference V exists between two points, l apart, along the length of the wire. IF R is the resistance of the wire between those two points, then the resistivity of its material is rho=(RA)/l .Besides the mobility (mu) of the free electrons inside a wire is defined as their drift velocity for a unit applied electric field. The radii of two wires of the same metal are in the ratio 1:2 The same potential difference is applied between two points at a distance l on each of the wires.The ratio between the drift velocities of the free electrons in two wires is

    A
    `1:1`
    B
    `1:2`
    C
    `2:1`
    D
    `1:4`

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    Ratio of lengths of two wires of same material is 2:3 and ratio of areas of cross section is 1 : 2 . Find the ratio of their drift velocities when:- they.are connected in series

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