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The drift velocity of electrons in a con...

The drift velocity of electrons in a conducting wire is of the order of 1 mm/s, yet the bulb glows very quickly after the switch is put on beause

A

The random speed of electons is very high, of the order of `10^(6)m//s`.

B

The electrons transfer their energy very quickly through collisions

C

Electric field is set up in the wire very quickly, producing a current through each cross section, almost instantaneously.

D

All of above

Text Solution

Verified by Experts

The correct Answer is:
C
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The drift velocity of electrons inside a conductor carrying current is of the order of 10^(-4)m//s , which means that the electrons flow very slowly through the conductor. Then why does it not require hours for a light bulb to turn on after pressing the switch ?

The drift velocity of the electrons in a copper wire of length 2 m under the application of a potential difference of 220V is 0.5ms^-1 . Their mobility ( in m^2v^-1s^-1 )

Knowledge Check

  • Assertion: Drift velocity of electrons developed in a current-carrying conductor is of the order of 10^(-4) m//s but current in the conductor is established almost instantly the switch is closed. Reason: Electric field in a conductor sets up with the speed of light.

    A
    If both assertion and reason are correct and reason is a correct explanation of the assertion
    B
    If both assertion and reason are correct but reason is not the correct explanation of the assertion
    C
    If assertion is correct but reason is incorrect
    D
    If assertion is incorrect but reason is correct

  • Assertion : The drift velocity of electrons in a metallic wire will decrease, if the temperature of the wire is increased. Reason : On increasing temperature, conductivity of metallic wire decreases.

    A
    If both assertion and reason are ture and reason is the correct explanation of assertion.
    B
    If both assertion and reason are true but reason is not the correct explanation of assertion.
    C
    If assertion is true but reason is false.
    D
    If assertion and reason both are false.

  • Assertion : The drift velocity of electrons in a metallic wire will decrease, if the temperature of the wire is increased. Reason : On increasing temperature, conductivity of metallic wire decreases.

    A
    If both assertion and reason are ture and reason is the correct explanation of assertion.
    B
    If both assertion and reason are true but reason is not the correct explanation of assertion.
    C
    If assertion is true but reason is false.
    D
    If assertion and reason both are false.

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    Explore conceptually related problems

    Calculate the drift velocity of electrons in an aluminium wire of radius 2 mm when a current o f5A passes through ti. ( Atomic weight of aliminium = 27 , density of aluminium = 2700 kg//m^(3), Avogadro number = 6 xx 10^(23) mol^(-1))

    Assertion : A wire of uniform cross-section and uniform resistivity is connected across an ideal cell. Now the length or wire is doubled keeping volume of wire constant. The drift velocity of electrons after stretching the wire becomes one fourth of what it was before streching the wire. Reason: If a wire (or uniform resistivity and uniform cross-section) of length l_(0) is stretched by a factor n, then its resistance becomes n^(2) times the one before stretching the wire (the volume of wire is kept constant in stretching process.) Fruther at constant potential difference, current is inversely proportional to resistance. Drift velocity of free electron is directly proportional to current and inversely proportional to cross-sectional area of current carrying wire.

    A :The drift velocity of electrons in a conductor is very small still current in a conductor is establised almost instantaneously on closing the switch. R: Electric field in the condutor sets up with speed of light.

    STATEMENT-1 : The drift velocity of electrons in a metallic wire will decrease, if the temperature of the wire is increased. and STATEMENT-2 : On increasing the temperature of the wire , conductivity of metallic wire decreases.

    Statement I: A wire of uniform cross-section and uniform resistivity is connected across an ideal cell. Now the length of the wire is doubled keeping volume of the wire constant. The drift velocity of electrons after stretching the wire becomes one-fouth of what it was before stretching the wire. Statement II: If a wire (of uniform resistivity and uniform cross section) of length l_0 is stretched to length nl_0 , then its resistance becomes n^2 times of what it was before stretching the wire (the volume of wire is kept constant in stretching process). Further at constant potential difference, current is inversely proportional to resistance. Finally, drift velocity of free electron is directly proportional to current and inversely proportional to cross-sectional area of current carrying wire.

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