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(A) Statement $(A)$ is true: In the absence of an external electric field,free electrons move randomly in all directions due to thermal energy. Betwee

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$A$ and $B$ are true

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(A) Statement $(A)$ is true: In the absence of an external electric field,free electrons move randomly in all directions due to thermal energy. Between two successive collisions,there is no external force acting on the electron,so it moves in a straight line at a constant velocity.Statement $(B)$ is true: When an electric field $E$ is applied,the electrons experience a force $F = -eE$. This force causes a constant average acceleration $a = -eE/m$. The drift velocity is defined as $v_d = a	au$,where $	au$ is the average relaxation time. Since $a$ and $	au$ are constant for a given conductor and temperature,the drift velocity $v_d$ is independent of time.

Similar Questions

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:

Drift speed of electrons,when $1.5 \, A$ of current flows in a copper wire of cross-section $5 \, mm^2$,is $v$. If the electron density in copper is $9 \times 10^{28} \, m^{-3}$,the value of $v$ in $mm/s$ is close to (Take charge of electron to be $1.6 \times 10^{-19} \, C$).

$A$ current of $5\, A$ passes through a copper conductor (resistivity $= 1.7 \times 10^{-8}\, \Omega \, m$) of radius of cross-section $5\, mm$. Find the mobility of the charges if their drift velocity is $1.1 \times 10^{-3}\, m/s$.

There are $0.8 \times 10^{23}$ free electrons $/ cm^3$ in copper. If a $0.2 \, A$ current is flowing in a copper wire, then the drift velocity of electrons will be, given the cross-sectional area of the wire is $0.01 \, cm^2$.

Mobility of free electrons in a conductor is

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