The ratio of the radii of two circular coils is \(1:2\). The ratio of currents in the respective coils such that the same magnetic moment is produced at the centre of each coil is:
1. \(4:1\)
2. \(2:1\)
3. \(1:2\)
4. \(1:4\)
Assertion (A): | Magnetic field due to an infinite straight conductor varies inversely as the distance from it. |
Reason (R): | The magnetic field at the center of the circular coil is zero. |
1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
3. | (A) is True but (R) is False. |
4. | Both (A) and (R) are False. |
A. | decreasing the number of turns. |
B. | increasing the magnetic field. |
C. | decreasing the area of the coil. |
D. | decreasing the torsional constant of the spring. |
1. | (B) and (C) only |
2. | (C) and (D) only |
3. | (A) and (C) only |
4. | (B) and (D) only |
Statement I: | The electric force changes the speed of the charged particle and hence changes its kinetic energy: whereas the magnetic force does not change the kinetic energy of the charged particle. |
Statement II: | The electric force accelerates the positively charged particle perpendicular to the direction of electric field. The magnetic force accelerates the moving charged particle along the direction of magnetic field. |
1. | Both Statement I and Statement II are correct. |
2. | Both Statement I and Statement II are incorrect. |
3. | Statement I is correct and Statement II is incorrect. |
4. | Statement I is incorrect and Statement II is correct. |
1. | kinetic energy changes |
2. | kinetic energy remains constant |
3. | speed changes |
4. | momentum remains constant |
Assertion (A): | \(\alpha\)-particle enters a uniform magnetic field perpendicularly with the same speed, then the time period of revolution of the \(\alpha\)-particle is double that of a proton. | If a proton and an
Reason (R): | In a magnetic field, the time period of revolution of a charged particle is directly proportional to mass. |
1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
3. | (A) is True but (R) is False. |
4. | Both (A) and (R) are False. |
1. | \(0\) | 2. | \(1.2\times 10^{-4}~\text{T}\) |
3. | \(2.1\times 10^{-4}~\text{T}\) | 4. | None of these |
An element \(\Delta l=\Delta x \hat{i}\) is placed at the origin and carries a large current of \(I=10\) A (as shown in the figure). What is the magnetic field on the \(y\text-\)axis at a distance of \(0.5\) m? \((\Delta x=1~\text{cm})\)
1. | \(6\times 10^{-8}~\text{T}\) | 2. | \(4\times 10^{-8}~\text{T}\) |
3. | \(5\times 10^{-8}~\text{T}\) | 4. | \(5.4\times 10^{-8}~\text{T}\) |
A long solenoid carrying a current produces a magnetic field \(B\) along its axis.
If the current is doubled and the number of turns per cm is halved, what will be the new value of the magnetic field?
1. \(B/2\)
2. \(B\)
3. \(2B\)
4. \(4B\)
What properties will a galvanometer that is acting as a voltmeter have?
1. | high resistance in series with its coil | 2. | low resistance in parallel with its coil |
3. | low resistance in series with its coil | 4. | high resistance in parallel with its coil |