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:  Current & Current Density |
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Level 2: 60%+
NEET - 2024
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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:  Current & Current Density |
 83%
Level 1: 80%+
NEET - 2020
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A silicon wafer of \(\mathrm{n}\)-type material with a cross-sectional area of \(3.14\times 10^{-6} \) m2, a conductivity of \(5.8\times 10^{7} \) siemens per metre, and an electron mobility of \(0.0032\) m2V–1s–1 is subjected to an electric field of \(20\) milli-V/m. (neglect hole concentration)
Match the items in Column-I with those in Column-II:

Column-I Column-II
(A) The electron concentration in the wafer is (P) \(1.16\times 10^6\) SI units
(B) The current density in the wafer is (Q) \(3.64\) SI units
(C) The current flowing through the wafer is (R) \(6.4\times 10^{-5}\) SI units
(D) The drift velocity of electrons is (S) \(1.13\times 10^{29}\) SI units
 
1. A(P), B(Q), C(R), D(S)
2. A(P), B(S), C(R), D(Q)
3. A(S), B(P), C(Q), D(R)
4. A(Q), B(P), C(R), D(S)
Subtopic:  Current & Current Density |
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When a current \(i\) flows through a conductor, the drift velocity of free electrons is \(v.\) If the current is increased to \(2i,\) and the cross-sectional area of the conductor is doubled, what will be the new drift velocity of the free electrons?
1. \(\dfrac{v}{4}\) 2. \(\dfrac{v}{2}\)
3. \(v\) 4. \(4v\)
Subtopic:  Current & Current Density |
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Drift velocity \(v_{d}\) varies with the intensity of the electric field as:

1. \(v_{d}\propto E^{0}\) 2. \(v_{d}\propto E\)
3. \(v_{d}\propto E^{-1}\) 4. \(v_{d}\propto E^{1/2}\)
Subtopic:  Current & Current Density |
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