- 1(current)
Q. No.Current density is the current crossing per unit area. Consider a cylindrical wire of uniform cross-section \(A,\) carrying a current \(I.\) Imagine a cross-section formed by a "\(30^\circ\)-cut" as shown (the wire is not really cut). The current density perpendicular to this cross-section is:
| 1. | \(\dfrac{I}{A}\) | 2. | \(\dfrac{I}{A}~\cos30^\circ\) |
| 3. | \(\dfrac{2I}{A}\) | 4. | \(\dfrac{I}{A}~\sin30^\circ\) |
Subtopic: Â Current & Current Density |
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A beam of electrons emitted from the electron gun \(G\) is accelerated by an electric field \(E.\) The area of cross-section of the beam remains constant. As the beam moves away from \(G,\)
Choose the correct option from the options given below:
| (A) | the speed of the electrons increases |
| (B) | the current constituted by the beam increases |
| (C) | the number of electrons per unit volume in the beam increases |
| (D) | the number of electrons per unit volume in the beam decreases |
| 1. | (A), (B) and (C) only |
| 2. | (A) and (D) only |
| 3. | (B) and (D) only |
| 4. | (B), (C) and (D) only |
Subtopic: Â Current & Current Density |
From NCERT
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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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The current flowing through the resistance \(R_1\), when \(R_1=R_2\) and \(R_3=R_4\) is:
| 1. | \(\frac{V}{4\left(R_1+R_3\right)}\) | 2. | \(\frac{2 V}{\left(R_1+R_3\right)}\) |
| 3. | \(\frac{V}{\left(R_1+R_3\right)}\) | 4. | \(\frac{V}{2\left(R_1+R_3\right)}\) |
Subtopic: Â Current & Current Density |
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- 1(current)
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