Q. No.A metallic rod of mass per unit length of \(0.5\) kgm–1 is lying horizontally on a smooth inclined plane which makes an angle of \(30^\circ\) with the horizontal. The rod is not allowed to slide down by flowing a current through it when a magnetic field of induction of \(0.25\) T is acting on it in the vertical direction. What is the current flowing through the rod to keep it stationary?
1.
\(7.14\) A
2.
\(5.98\) A
3.
\(14.76\) A
4.
\(11.32\) A
A closely wound solenoid of 2000 turns and area of cross-section 1.5 × 10–4 m2 carries a current of 2.0 A. It is suspended through its centre and perpendicular to its length, allowing it to turn in a horizontal plane in a uniform magnetic field 1.5 × 10–2 T , making an angle of 30° with the axis of the solenoid. The torque on the solenoid will be?
1. 3 × 10–3 N-m
2. 4.5 × 10–3 N-m
3. 1.5 × 10–2 N-m
4. 3 × 10–2 N-m
Moving perpendicular to field \(B\), a proton and an alpha particle both enter an area of uniform magnetic field \(B\). If the kinetic energy of the proton is \(1~\text{MeV}\) and the radius of the circular orbits for both particles is equal, the energy of the alpha particle will be:
1. \(4~\text{MeV}\)
2. \(0.5~\text{MeV}\)
3. \(1.5~\text{MeV}\)
4. \(1~\text{MeV}\)
| 1. | \({1 \over 499}G\) | 2. | \({499 \over 500}G\) |
| 3. | \({1 \over 500}G\) | 4. | \({500 \over 499}G\) |
| 1. | can be in equilibrium in one orientation |
| 2. | can be in equilibrium in two orientations, both the equilibrium states are unstable |
| 3. | can be in equilibrium in two orientations, one stable while the other is unstable |
| 4. | experiences a torque whether the field is uniform or non-uniform in all orientations |
A very long straight wire carries a current I. At the instant when a charge +Q at point P has velocity , as shown, the force on the charge is-
1. Along OX
2. Opposite to OY
3. Along OY
4. Opposite to OX
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. \(\frac{2R}{\sqrt3}\)
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