Solenoid

Q. Direction of magnetic field inside a solenoid is along the axis of solenoid.

1. False
2. True

Q. A solenoid of length $50cm$ with $600turns$ is connected to a cell and current through the solenoid is $\frac{20}{\pi }A$. Find magnetic field inside the solenoid (in central region). Assume solenoid is ideal

1. $9.6\times {10}^{-3}T$
2. $4.8\times {10}^{-3}T$
3. $2.4\times {10}^{-3}T$
4. $9.6\times {10}^{-7}T$

Q. What will be the magnetic field at any point lying outside a long solenoid of very small radius?

1. Similar to in region inside the solenoid
2. Can be approximated to zero
3. Very large and close to infinity
4. cannot be detrmined

Q. A long solenoid has 200 turns per cm and carries a current of 2.5 amps. The magnetic field at its centre is (${\mu }_0=4\pi \times {10}^{-7}weber/amp-m$)

1. $3.14\times {10}^{2}weber/m^2$
2. $6.28\times {10}^{-2}weber/m^2$
3. $9.42\times {10}^{-2}weber/m^2$
4. $12.56\times {10}^{-2}weber/m^2$

Q. A long solenoid has 200 turns per cm and carries a current of 2.5 amps. The magnetic field at its centre is (${\mu }_0=4\pi \times {10}^{-7}weber/amp-m$)

1. $3.14\times {10}^{2}weber/m^2$
2. $6.28\times {10}^{-2}weber/m^2$
3. $9.42\times {10}^{-2}weber/m^2$
4. $12.56\times {10}^{-2}weber/m^2$

Q. Solenoid of radius r & length l is shown in figure, current i is passed through it. Then,

1. r =l is necessary for $B={\mu }_{0}ni$
2. l >> r is necessary for $B={\mu }_{0}ni$
3. We can apply $B={\mu }_{0}ni$ even if winding is not tight.
4. r >> l is necessary for $B={\mu }_{0}ni$

Q. There are 50 turns of a wire in every $1cm$ length of a long solenoid. If a $4A$ current is flowing in the solenoid, the approximate value of magnetic field along its axis at an internal point and at one end will be respectively

1. $12.6\times {10}^{-3}\frac{Weber}{m^2},6.3\times {10}^{-3}\frac{Weber}{m^2}$
2. $12.6\times {10}^{-3}\frac{Weber}{m^2},25.1\times {10}^{-3}\frac{Weber}{m^2}$
3. $25.1\times {10}^{-3}\frac{Weber}{m^2},12.6\times {10}^{-3}\frac{Weber}{m^2}$
4. $25.1\times {10}^{-5}\frac{Weber}{m^2},6.3\times {10}^{-5}\frac{Weber}{m^2}$

Q. Direction of magnetic field inside a solenoid is along the axis of solenoid.

1. False
2. True

Q. Figure shows solenoid with 'n' turns per unit length and current 'i'. Magnetic field at P can be given as

1. ${\mu }_{0}ni[\frac{1}{\sqrt{5}}-\frac{1}{2\sqrt{2}}]$
2. $\frac{{\mu }_{0}ni}{\sqrt{2}}$
3. ${\mu }_{0}ni[\frac{1}{\sqrt{2}}-\frac{1}{2}]$
4. $\frac{{\mu }_{0}ni}{\sqrt{5}}$

Q. There are 50 turns of a wire in every $1cm$ length of a long solenoid. If a $4A$ current is flowing in the solenoid, the approximate value of magnetic field along its axis at an internal point and at one end will be respectively

1. $12.6\times {10}^{-3}\frac{Weber}{m^2},6.3\times {10}^{-3}\frac{Weber}{m^2}$
2. $12.6\times {10}^{-3}\frac{Weber}{m^2},25.1\times {10}^{-3}\frac{Weber}{m^2}$
3. $25.1\times {10}^{-3}\frac{Weber}{m^2},12.6\times {10}^{-3}\frac{Weber}{m^2}$
4. $25.1\times {10}^{-5}\frac{Weber}{m^2},6.3\times {10}^{-5}\frac{Weber}{m^2}$

Q. Two coaxial solenoids 1 and 2 of the same length are set so that one is inside the other. The number of turns per unit length are $n_1$ and $n_2$ . The currents $i_1$ and $i_2$ are flowing in opposite directions. The magnetic field inside the inner coil is zero. This is possible when?
[Roorkee 2000]

1. $i_1\ne i_{2}and{n}_1=n_2$
   
2. $i_1=i_{2}and{n}_1\ne n_2$
   
3. $i_1=i_{2}and{n}_1=n_2$
   
4. $i_1{n}_1=i_2{n}_2$

Q. The field at any point lying outside the region occupied by a solenoid of very small radius is almost zero.

1. True
2. False