Q. No.The magnetic flux linked with a coil varies with time as \(\phi = 2t^2-6t+5,\) where \(\phi \) is in Weber and \(t\) is in seconds. The induced current is zero at:
| 1. | \(t=0\) | 2. | \(t= 1.5~\text{s}\) |
| 3. | \(t=3~\text{s}\) | 4. | \(t=5~\text{s}\) |
A coil having number of turns \(N\) and cross-sectional area \(A\) is rotated in a uniform magnetic field \(B\) with an angular velocity \(\omega\). The maximum value of the emf induced in it is:
1. \(\frac{NBA}{\omega}\)
2. \(NBAω\)
3. \(\frac{NBA}{\omega^{2}}\)
4. \(NBAω^{2}\)
In a circuit with a coil of resistance \(2~\Omega\), the magnetic flux changes from \(2.0\) Wb to \(10.0\) Wb in \(0.2~\text{s}\). The charge that flows in the coil during this time is:
1. \(5.0~\text{C}\)
2. \(4.0~\text{C}\)
3. \(1.0~\text{C}\)
4. \(0.8~\text{C}\)
The current in a coil varies with time \(t\) as \(I= 3 t^{2} +2t\). If the inductance of coil be \(10\) mH, the value of induced emf at \(t=2~\text{s}\) will be:
1. \(0.14~\text{V}\)
2. \(0.12~\text{V}\)
3. \(0.11~\text{V}\)
4. \(0.13~\text{V}\)
1. \(\frac{3 A_{0} B_{0}}{t}\)
2. \(\frac{4 A_{0} B_{0}}{t}\)
3. \(\frac{3 B_{0}}{A_{0} t}\)
4. \(\frac{4 B_{0}}{A_{0} t}\)
A bar magnet is released along the vertical axis of the conducting coil. The acceleration of the bar magnet is:
| 1. | greater than \(g\). | 2. | less than \(g\). |
| 3. | equal to \(g\). | 4. | zero. |
A wire loop is rotated in a magnetic field. The frequency of change of direction of the induced e.m.f. is:
| 1. | Twice per revolution | 2. | Four times per revolution |
| 3. | Six times per revolution | 4. | Once per revolution |
| Assertion (A): | The bar magnet falling vertically along the axis of the horizontal coil will be having acceleration less than \(g.\) |
| Reason (R): | Clockwise current induced in the coil. |
| 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. | \(5\) V | 2. | \(4\) V |
| 3. | \(3\) V | 4. | zero |
An aluminium ring \(B\) faces an electromagnet \(A\). If the current \(I\) through \(A\) can be altered, then:
| 1. | whether \(I\) increases or decreases, \(B\) will not experience any force. |
| 2. | if \(I\) decreases, \(A\) will repel \(B\). |
| 3. | if \(I\) increases, \(A\) will attract \(B\). |
| 4. | if \(I\) increases, \(A\) will repel \(B\). |
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