(B) $1$. The current $I$ flowing through the conductor is constant throughout because it is a series circuit.$2$. Current density $J = I/A$. Since the

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The current density is lower at $P$ than at $Q$.

(B) $1$. The current $I$ flowing through the conductor is constant throughout because it is a series circuit.$2$. Current density $J = I/A$. Since the cross-sectional area $A_P > A_Q$, the current density $J_P $3$. Electric field $E = J/\sigma = I/(A\sigma)$. Since $A_P > A_Q$, $E_P $4$. The rate of heat production per unit length is $dH/dx = I^2 R/dx = I^2 \rho / A$. Since $A_P > A_Q$, the rate of heat production is lower at $P$ than at $Q$.$5$. Therefore, the correct statement is that the current density is lower at $P$ than at $Q$ (Option $B$).

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

Easy

$A$ conductor of non-uniform cross-section is connected to a source of constant potential difference as shown in the figure. Then:

A
The electric field intensity is higher at $P$ than at $Q$.
B
The current density is lower at $P$ than at $Q$.
C
The rate of heat production per unit length is higher at $P$ than at $Q$.
D
The average kinetic energy of free electrons is higher at $P$ than at $Q$.

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Current Electricity

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Current Density, Drift Velocity and Mobility

$A$ 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$)

MediumTS EAMCET 2020

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The mechanism of the heat produced in a conductor when an electric current flows through it can be explained on the basis of

Easy

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$A$ current of $5\; A$ is passing through a non-linear magnesium wire of cross-section $0.04\; m^2$. At every point,the direction of current density is at an angle of $60^{\circ}$ with the unit vector of the area of cross-section. The magnitude of the electric field at every point of the conductor is .... $V/m$ (Resistivity of magnesium is $\rho = 44 \times 10^{-8}\, \Omega m$).

DifficultJEE MAIN 2021

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$A$ potential difference of $V$ is applied at the ends of a copper wire of length $l$ and diameter $d$. On doubling only $d$,drift velocity

Easy

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At room temperature,copper has a free electron density of $8.4 \times 10^{28} \, m^{-3}$. The copper conductor has a cross-section of $10^{-6} \, m^2$ and carries a current of $5.4 \, A$. The electron drift velocity in copper is:

Easy

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$A$ conductor of non-uniform cross-section is connected to a source of constant potential difference as shown in the figure. Then:

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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$)

The mechanism of the heat produced in a conductor when an electric current flows through it can be explained on the basis of

$A$ potential difference of $V$ is applied at the ends of a copper wire of length $l$ and diameter $d$. On doubling only $d$,drift velocity

At room temperature,copper has a free electron density of $8.4 \times 10^{28} \, m^{-3}$. The copper conductor has a cross-section of $10^{-6} \, m^2$ and carries a current of $5.4 \, A$. The electron drift velocity in copper is:

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