Q. No.A uniform electric field and a uniform magnetic field are acting in the same direction in a certain region. If an electron is projected in the region such that its velocity is pointed along the direction of fields, then the electron:
1.
speed will decrease
2.
speed will increase
3.
will turn towards the left of the direction of motion
4.
will turn towards the right of the direction of motion
Two charged particles having charges q and mass m are moving on circular paths in same uniform magnetic field with speed v and 2v. Ratio of their angular velocities are
1.
2.
3.
4.
A circular current-carrying coil has a radius \(R.\) The distance from the centre of the coil, on the axis, where \(B\) will be \(\frac18\) of its value at the centre of the coil is:
1. \(\frac{R}{\sqrt3}\)
2. \(\sqrt3R\)
3. \(2\sqrt3R\)
4. \(\frac{2R}{\sqrt3}\)
1. 1 A
2. 58 A
3. 58 mA
4. 30 mA
| 1. | Angle between \(\vec v\) and \(\vec {B}\) is necessarily \(90^{\circ}\). |
| 2. | Angle between \(\vec v\) and \(\vec {B}\) can have any value other than \(90^{\circ}\). |
| 3. | Angle between \(\vec v\) and \(\vec {B}\) can have any value other than zero and \(180^{\circ}\). |
| 4. | Angle between \(\vec v\) and \(\vec {B}\) is either zero or \(180^{\circ}\). |
Magnetic field at point O will be: (assume straight wire segments are infinite)
1. \(\frac{\mu_{_0}l}{2R}\) interior
2. \(\frac{\mu_{_0}l}{2R}\) exterior
3. \(\frac{\mu_{_0}l}{2R}1-\frac{l}{\pi}\) interior
4. \(\frac{\mu_{_0}l}{2R}1-\frac{l}{\pi}\) exterior
A square loop is made by a uniform conductor wire as shown in the figure,
The net magnetic field at the centre of the loop if the side length of the square is a:
1. \(\frac{\mu_{_0}i}{2a}\)
2. zero
3. \(\frac{\mu_{_0}i^2}{a^2}\)
4. None of these
| 1. | low resistance in series with its coil |
| 2. | low resistance in parallel with its coil |
| 3. | high resistance in series with its coil |
| 4. | high resistance in parallel with its coil |
A galvanometer can be changed into an ammeter by using:
| 1. | low resistance shunt in series |
| 2. | low resistance shunt in parallel |
| 3. | high resistance shunt in series |
| 4. | high resistance shunt in parallel |
A cylindrical conductor of radius \(R\) is carrying a constant current. The plot of the magnitude of the magnetic field \(B\) with the distance \(d\) from the centre of the conductor is correctly represented by the figure:
| 1. |  |
2. |  |
| 3. |  |
4. |  |
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