(C) The current $I$ flowing through any cross-section of a conductor in a steady state is constant,so $I$ is the same at all points.Using the relation

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Drift speed of electrons at point $A$ is lesser than that at point $B$.

(C) The current $I$ flowing through any cross-section of a conductor in a steady state is constant,so $I$ is the same at all points.Using the relation $I = neA V_d$,where $n$ is the number density of electrons,$e$ is the charge of an electron,$A$ is the cross-sectional area,and $V_d$ is the drift speed.Since $I$,$n$,and $e$ are constant,we have $V_d \propto \frac{1}{A}$.As the cross-sectional area $A$ decreases along the wire from $A$ to $B$,the drift speed $V_d$ must increase.Therefore,the drift speed at point $A$ is less than the drift speed at point $B$,i.e.,$(V_d)_A < (V_d)_B$.

Class 12 Physics Current Electricity Current Density, Drift Velocity and Mobility

Medium

Suppose a current-carrying wire has a cross-sectional area that gradually becomes smaller along the wire,having the shape of a very long cone as shown in the figure. Choose the correct statement.

A
Electric current is different in different portions of the wire.
B
Electric field at point $A$ is the same as that of point $B$.
C
Drift speed of electrons at point $A$ is lesser than that at point $B$.
D
Drift speed of electrons at point $A$ is the same as that at point $B$.

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Current Electricity

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Current Density, Drift Velocity and Mobility

$A$ current of $2\,A$ flows through a wire of cross-sectional area $25.0\,mm^2$. The number of free electrons per cubic meter is $2.0 \times 10^{28}$. The drift velocity of the electrons is $...............\times 10^{-6}\,ms^{-1}$ (given,charge on electron $= 1.6 \times 10^{-19}\,C$).

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Current density in a cylindrical wire of radius $R$ is given as $J = \begin{cases} J_0 \left( \frac{x}{R} - 1 \right) & 0 \leqslant x < \frac{R}{2} \\ J_0 \frac{x}{R} & \frac{R}{2} \leqslant x \leqslant R \end{cases}$. The current flowing in the wire is:

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An ionization chamber with parallel conducting plates as anode and cathode has $5 \times 10^7$ electrons and the same number of singly-charged positive ions per $cm^3$. The electrons are moving at $0.4\, m/s$. The current density from anode to cathode is $4\,\mu A/m^2$. The velocity of positive ions moving towards cathode is ............. $m/s$. [$AIPMT$ $1992$]

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Charge passing through a conductor of cross-section area $A=0.3 \,m^2$ is given by $q=3 t^2+5 t+2$ in coulomb,where $t$ is in second. What is the value of drift velocity at $t=2 \,s$ ? (Given,$n=2 \times 10^{25} / m^3$ )

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There is a current of $1.344 \, A$ in a copper wire whose area of cross-section normal to the length of the wire is $1 \, mm^2$. If the number of free electrons per $cm^3$ is $8.4 \times 10^{22}$, then the drift velocity would be

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Suppose a current-carrying wire has a cross-sectional area that gradually becomes smaller along the wire,having the shape of a very long cone as shown in the figure. Choose the correct statement.

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$A$ current of $2\,A$ flows through a wire of cross-sectional area $25.0\,mm^2$. The number of free electrons per cubic meter is $2.0 \times 10^{28}$. The drift velocity of the electrons is $...............\times 10^{-6}\,ms^{-1}$ (given,charge on electron $= 1.6 \times 10^{-19}\,C$).

Current density in a cylindrical wire of radius $R$ is given as $J = \begin{cases} J_0 \left( \frac{x}{R} - 1 \right) & 0 \leqslant x < \frac{R}{2} \\ J_0 \frac{x}{R} & \frac{R}{2} \leqslant x \leqslant R \end{cases}$. The current flowing in the wire is:

Charge passing through a conductor of cross-section area $A=0.3 \,m^2$ is given by $q=3 t^2+5 t+2$ in coulomb,where $t$ is in second. What is the value of drift velocity at $t=2 \,s$ ? (Given,$n=2 \times 10^{25} / m^3$ )

There is a current of $1.344 \, A$ in a copper wire whose area of cross-section normal to the length of the wire is $1 \, mm^2$. If the number of free electrons per $cm^3$ is $8.4 \times 10^{22}$, then the drift velocity would be

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