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When a Current is Established in a Wire, the Free Electrons Drift in the Direction Opposite to the Current. Does the Number of Free Electrons in the Wire Continuously Decrease?

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प्रश्न

When a current is established in a wire, the free electrons drift in the direction opposite to the current. Does the number of free electrons in the wire continuously decrease?

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उत्तर

No, the number of electrons in the wire remains constant. The electrons that drift and move to the positive terminal of the battery, under the influence of the external electric field, are replaced by the battery in the circuit. As a result, the total number of free electrons in the wire is always constant.

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पाठ 32: Electric Current in Conductors - Short Answers [पृष्ठ १९६]

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एचसी वर्मा Concepts of Physics Volume 1 and 2 [English]
पाठ 32 Electric Current in Conductors
Short Answers | Q 7 | पृष्ठ १९६

संबंधित प्रश्‍न

What is its relation with relaxation time?


Write its (‘mobility’ of charge carriers) S.I. unit


Estimate the average drift speed of conduction electrons in a copper wire of cross-sectional area 1.0 × 10−7 m2 carrying a current of 1.5 A. Assume the density of conduction electrons to be 9 × 1028 m−3


A wire whose cross-sectional area is increasing linearly from its one end to the other, is connected across a battery of V volts.
Which of the following quantities remain constant in the wire?
(a) drift speed
(b) current density
(c) electric current
(d) electric field

On the basis of electron drift, derive an expression for resistivity of a conductor in terms of number density of free electrons and relaxation time. On what factors does resistivity of a conductor depend?


Why alloys like constantan and manganin are used for making standard resistors?


When electrons drift in a metal from lower to higher potential, does it mean that all the free electrons of the metal are moving in the same direction?


Consider the following statements.
(A) Free-electron density is different in different metals.
(B) Free-electron density in a metal depends on temperature.

Peltier Effect is caused _______________ .


Obtain the expression for the current flowing through a conductor having number density of the electron n, area of cross-section A in terms of the drift velocity vd


When a current I is set up in a wire of radius r, the drift velocity is vd· If the same current is set up through a wire of radius 2 r, the drift velocity will be:


Metals are good conductor of heat than insulator because


An electric bulb.is rated 220 v and 100 watt power consumed by it when operated on 'no volt is:-


The identical conductors maintained at same temperature are given potential difference in the ratio 1 : 2. Then the ratio of their drift velocities is ______.


The relaxation time τ is nearly independent of applied E field whereas it changes significantly with temperature T. First fact is (in part) responsible for Ohm’s law whereas the second fact leads to variation of ρ with temperature. Elaborate why?


Derive an expression for resistivity of a conductor in terms of the number density of charge carriers in the conductor and relaxation time.


The potential difference applied across a given conductor is doubled. How will this affect (i) the mobility of electrons and (ii) the current density in the conductor? Justify your answers.


A potential difference (V) is applied across a conductor of length 'L' and cross-sectional area 'A'.

How will the drift velocity of electrons and the current density be affected if another identical conductor of the same material were connected in series with the first conductor? Justify your answers.


Two conductors, made of the same material have equal lengths but different cross-sectional areas A1 and A2 (A1 > A2). They are connected in parallel across a cell. Show that the drift velocities of electrons in two conductors are equal.


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