A uniform wire of diameter $$d$$ carries a current of $$100~\text{mA}$$ when the mean drift velocity of electrons in the wire is $$v.$$ For a wire of diameter $${\dfrac{d}{2}}$$ of the same material to carry a current of $$200~\text{mA},$$ the mean drift velocity of electrons in the wire is:
 1 $$4v$$ 2 $$8v$$ 3 $$v$$ 4 $$2v$$
Subtopic: Â Current & Current Density |
Â 65%
From NCERT
NEET - 2024
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A uniform metal wire of length $$l$$ has $$10~\Omega$$ resistance. Now this wire is stretched to a length $$2l$$  and then bent to form a perfect circle. The equivalent resistance across any arbitrary diameter of that circle is:
 1 $$10~\Omega$$ 2 $$5~\Omega$$ 3 $$40~\Omega$$ 4 $$20~\Omega$$
Subtopic: Â Current & Current Density |
From NCERT
NEET - 2024
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A copper wire of radius $$1$$ mm contains $$10^{22}$$ free electrons per cubic metre. The drift velocity for free electrons when $$10$$ A current flows through the wire will be:
(Given, charge on electron = $$1.6\times10^{-19}$$ C)
1. $$\dfrac{6.25\times10^4}{\pi}$$ m/s
2. $$\dfrac{6.25}{\pi}\times10^3$$ m/s
3. $$\dfrac{6.25}{\pi}$$ m/s
4. $$\dfrac{6.25\times10^5}{\pi}$$ m/s
Subtopic: Â Current & Current Density |
Â 71%
From NCERT
NEET - 2023
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A copper wire of length $$10$$ m and radius $$\left({10^{-2}/\sqrt{\pi}}\right)$$ m has an electrical resistance of $$10~\Omega.$$ The current density in the wire for an electric field strength of $$10$$ (V/m) is:
1. $$10^{5}$$ A/m2
2. $$10^{4}$$ A/m2
3. $$10^{6}$$ A/m2
4. $$10^{-5}$$ A/m2
Subtopic: Â Current & Current Density |
Â 66%
From NCERT
NEET - 2022
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Match Column I and Column II with appropriate relations.

 Column I Column II (A) Drift Velocity (P) $$\dfrac{ \mathrm{m}}{\mathrm{ne}^2 \rho}$$ (B) Electrical Resistivity (Q) $$nev_d$$ (C) Relaxation Period (R) $$\dfrac{ \mathrm{eE}}{\mathrm{m}} \tau$$ (D) Current Density (S) $$\dfrac{E}{J}$$

 (A) (B) (C) (D) 1. (R) (P) (S) (Q) 2. (R) (Q) (S) (P) 3. (R) (S) (P) (Q) 4. (R) (S) (Q) (P)
Subtopic: Â Current & Current Density |
Â 55%
From NCERT
NEET - 2021
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A charged particle having drift velocity of $$7.5\times10^{-4}~\text{ms}^{-1}$$ in an electric field of $$3\times10^{-10}~\text{Vm}^{-1}$$, has mobility of:
1. $$2.5\times 10^{6}~\text{m}^2\text{V}^{-1}\text{s}^{-1}$$
2. $$2.5\times 10^{-6}~\text{m}^2\text{V}^{-1}\text{s}^{-1}$$
3. $$2.25\times 10^{-15}~\text{m}^2\text{V}^{-1}\text{s}^{-1}$$
4. $$2.25\times 10^{15}~\text{m}^2\text{V}^{-1}\text{s}^{-1}$$

Subtopic: Â Current & Current Density |
Â 82%
From NCERT
NEET - 2020
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