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प्रश्न
A conductor of length ‘l’ is connected to a dc source of potential ‘V’. If the length of the conductor is tripled by gradually stretching it, keeping ‘V’ constant, how will (i) drift speed of electrons and (ii) resistance of the conductor be affected? Justify your answer.
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उत्तर
V = constant
l’ = 3l
(i) Drift speed of electrons `= V/("nel" rho)`
Where n is number of electrons
e is charge on electron
l is the length of the conductor
and ρ is the resistivity of conductor.
So, when length is tripled, drift velocity gets one-third.
(ii) Resistance of the conductor is given as
`R =rho l/A`
When length is tripled area of cross-section is reduced to `A/3`
Hence, `R = rho (l')/(A') = rho(3l)/(A/3) = 9rhol/A =9R`
Thus, new resistance will be 9 times the original.
संबंधित प्रश्न
The number density of free electrons in a copper conductor is 8.5 × 1028 m−3. How long does an electron take to drift from one end of a wire 3.0 m long to its other end? The area of cross-section of the wire is 2.0 × 10−6 m2 and it is carrying a current of 3.0 A.
(a) drift speed
(b) current density
(c) electric current
(d) electric field
Electrons are emitted by a hot filament and are accelerated by an electric field, as shown in the figure. The two stops at the left ensure that the electron beam has a uniform cross-section.
Consider the following statements.
(A) Free-electron density is different in different metals.
(B) Free-electron density in a metal depends on temperature.
Seebeck Effect is caused _____________ .
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 _______________ .
The drift velocity of a free electron inside a conductor 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 ______.
Define relaxation time.
Derive an expression for resistivity of a conductor in terms of the number density of charge carriers in the conductor and relaxation time.
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.
