Q. No.The amount of charge \(Q\) passed in time \(t\) through a cross-section of a wire is \(Q=(7t^{2}+4t+1)~\text{C}.\) The value of current at time \(t= 6\) seconds is:
1. \( 38~ \text{A} \)
2. \( 27~ \text{A} \)
3. \( 104~ \text{A} \)
4. \( 88~ \text{A}\)
1. \( 38~ \text{A} \)
2. \( 27~ \text{A} \)
3. \( 104~ \text{A} \)
4. \( 88~ \text{A}\)
Subtopic: Current & Current Density |
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The electric current through a wire varies with time as shown in the figure.
The total charge flown across any cross-section of the wire in the time interval \((0 \text-T)\) is:
The total charge flown across any cross-section of the wire in the time interval \((0 \text-T)\) is:
| 1. | \( {i}_{0}T\) | 2. | \( \dfrac{{i}_{0}T}{2}\) |
| 3. | \( \dfrac{{i}_{0}T}{3}\) | 4. | \( \dfrac{{i}_{0}T}{\sqrt{2}}\) |
Subtopic: Current & Current Density |
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Level 2: 60%+
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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: Current & Current Density |
50%
Level 3: 35%-60%
NEET - 2024
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When no current is passed through a conductor,
| (a) | the free electrons do not move. |
| (b) | the average speed of a free electron over a large period of time is zero. |
| (c) | the average velocity of a free electron over a large period of time is zero. |
| (d) | the average of the velocities of all the free electrons at an instant is zero. |
Choose the correct option:
| 1. | (a) only | 2. | (b), (c) |
| 3. | (c), (d) | 4. | (a), (d) |
Subtopic: Current & Current Density |
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Level 3: 35%-60%
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Choose the incorrect statement out of the following:
| 1. | the relation \(V\text=IR\) applies to ohmic as well as non-ohmic conductors. |
| 2. | the relation \(\vec{E} = \rho \vec{j}\) applies to all conducting devices, where \(\vec{E}\) is the electric field, \(\vec{j}\) is the current density, and \(\rho\) is resistivity. |
| 3. | the resistance of an ohmic conductor is constant at a given temperature. |
| 4. | the resistance of a non-ohmic conductor is a function of the applied voltage. |
Subtopic: Current & Current Density |
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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
1. \(10^{5}\) A/m2
2. \(10^{4}\) A/m2
3. \(10^{6}\) A/m2
4. \(10^{-5}\) A/m2
Subtopic: Current & Current Density |
69%
Level 2: 60%+
NEET - 2022
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Consider a current carrying wire (current \(\text{I}\)) in the shape of a circle. Note that as the current progresses along the wire, the direction of \(\text{j}\) (current density) changes in an exact manner, while the current \(\text{I}\) remains unaffected. The agent that is essentially responsible for it is:
| 1. | source of emf. |
| 2. | the electric field produced by charges accumulated on the surface of the wire. |
| 3. | the charges just behind a given segment of wire which push them just the right way by repulsion. |
| 4. | the charges ahead. |
Subtopic: Current & Current Density |
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Level 2: 60%+
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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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Match Column-I and Column-II with appropriate relations.
| Column-I | Column-II | ||
| \(\mathrm{(A)}\) | Drift Velocity | \(\mathrm{(P)}\) | \(\dfrac{{m}}{{ne}^2 \rho}\) |
| \(\mathrm{(B)}\) | Electrical Resistivity | \(\mathrm{(Q)}\) | \(nev_d\) |
| \(\mathrm{(C)}\) | Relaxation Period | \(\mathrm{(R)}\) | \(\dfrac{ {eE}}{{m}} \tau\) |
| \(\mathrm{(D)}\) | Current Density | \(\mathrm{(S)}\) | \(\dfrac{E}{J}\) |
| \(\mathrm{(A)}\) | \(\mathrm{(B)}\) | \(\mathrm{(C)}\) | \(\mathrm{(D)}\) | |
| 1. | \(\mathrm{(R)}\) | \(\mathrm{(P)}\) | \(\mathrm{(S)}\) | \(\mathrm{(Q)}\) |
| 2. | \(\mathrm{(R)}\) | \(\mathrm{(Q)}\) | \(\mathrm{(S)}\) | \(\mathrm{(P)}\) |
| 3. | \(\mathrm{(R)}\) | \(\mathrm{(S)}\) | \(\mathrm{(P)}\) | \(\mathrm{(Q)}\) |
| 4. | \(\mathrm{(R)}\) | \(\mathrm{(S)}\) | \(\mathrm{(Q)}\) | \(\mathrm{(P)}\) |
Subtopic: Current & Current Density |
59%
Level 3: 35%-60%
NEET - 2021
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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 |
78%
Level 2: 60%+
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