(A) In the absence of an electric current,the free electrons in a conductor are in a state of random motion,similar to molecules in a gas. Their avera

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(A) In the absence of an electric current,the free electrons in a conductor are in a state of random motion,similar to molecules in a gas. Their average velocity is zero,meaning they do not have any net velocity in a specific direction. As a result,there is no net magnetic force on the free electrons in a magnetic field. When a current is passed,the free electrons acquire a drift velocity in a definite direction,and consequently,a magnetic force acts on them (provided the magnetic field has a component perpendicular to the direction of flow).

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

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Assertion: Free electrons always keep on moving in a conductor,even then no magnetic force acts on them in a magnetic field unless a current is passed through it.
Reason: The average velocity of free electrons is zero.

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A
If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
B
If both Assertion and Reason are correct,but Reason is not the correct explanation of Assertion.
C
If Assertion is correct but Reason is incorrect.
D
If both the Assertion and Reason are incorrect.

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Current Electricity

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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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There is a current of $40 \ A$ in a wire of cross-sectional area $10^{-6} \ m^2$. If the number of free electrons per $m^3$ is $10^{29}$,then the drift velocity will be:

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$A$ conductor of length $100 \, cm$ and area of cross-section $1 \, mm^2$ carries a current of $5 \, A$. If the resistivity of the material of the conductor is $3.0 \times 10^{-8} \, \Omega \cdot m$, then the electric field across the conductor is (in $ \, V/m$)

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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 $0.01 \, cm^2$.

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When $5\ V$ potential difference is applied across a wire of length $0.1\ m$,the drift speed of electrons is $2.5 \times 10^{-4} \ m/s$. If the electron density in the wire is $8 \times 10^{28} \ m^{-3}$,the resistivity of the material is close to:

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Assertion: Free electrons always keep on moving in a conductor,even then no magnetic force acts on them in a magnetic field unless a current is passed through it.Reason: The average velocity of free electrons is zero.

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There is a current of $40 \ A$ in a wire of cross-sectional area $10^{-6} \ m^2$. If the number of free electrons per $m^3$ is $10^{29}$,then the drift velocity will be:

$A$ conductor of length $100 \, cm$ and area of cross-section $1 \, mm^2$ carries a current of $5 \, A$. If the resistivity of the material of the conductor is $3.0 \times 10^{-8} \, \Omega \cdot m$, then the electric field across the conductor is (in $ \, V/m$)

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 $0.01 \, cm^2$.

When $5\ V$ potential difference is applied across a wire of length $0.1\ m$,the drift speed of electrons is $2.5 \times 10^{-4} \ m/s$. If the electron density in the wire is $8 \times 10^{28} \ m^{-3}$,the resistivity of the material is close to:

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Assertion: Free electrons always keep on moving in a conductor,even then no magnetic force acts on them in a magnetic field unless a current is passed through it.
Reason: The average velocity of free electrons is zero.