Solenoid and Bar Magnet

Q.

Statements given below are incorrect. Write the correct statements.

The magnetic lines of force around a very weak magnet are not close continuous curves.

Q.

A bar magnet has a pole strength of 15 Am. If the distance from its center to either of the poles is 15 cm, arrange the following steps in sequential order to find its magnetic moment in the SI unit.

(A) Write the given value of pole strength (m) of the magnet.

(B) Substitute the values in the above formula to get the value of M.

(C) Find the value of length(l) of the magnet from the problem and convert it into SI units.

(D) Write the required formula, i.e., magnetic moment, $\left(M\right)=m\times 2l$.

1. ACBD

2. CABD

3. ADCB

4. DBAC

Q. The distance of two points on the axis of a magnet from its centre is 10 cm and 20 cm respectively. The ratio of magnetic intensity at these points is 12.5 : 1. The length of the magnet will be

1. 5 cm
2. 25 cm
3. 10 cm
4. 20 cm

Q. Points A and B are situated along the extended axis of 2 cm long bar magnet at a distance x and 2x cm respectively. From the pole nearer to the points, the ratio of the magnetic field at A and B will be

1. 4 : 1 exactly
2. 4 : 1 approx
3. 8 : 1 exactly
4. 8 : 1 approx

Q. Two identical short bar magnets, each having magnetic moment of $10A{m}^2$, are arranged such that their axial lines are perpendicular to each other and their centres be along the same straight line in a horizontal plane. If the distance between their centres is 0.2 m, the resultant magnetic induction at a point midway between them is $({\mu }_0=4\pi \times {10}^{-7}H{m}^{-1})$

1. $\sqrt{2}\times {10}^{-7}$ Tesla
2. $\sqrt{5}\times {10}^{-7}$ Tesla
3. $\sqrt{2}\times {10}^{-3}$ Tesla
4. $\sqrt{5}\times {10}^{-3}$ Tesla

Q. A bar magnet of length 3 cm has points A and B along its axis at distances of 24 cm and 48 cm on the opposite sides. Ratio of magnetic fields at these points will be

1. 8
2. $\frac{1}{2\sqrt{2}}$
3. $3$
4. $4$

Q. A small bar magnet has a magnetic moment $1.2A-m^2$. The magnetic field at a distance 0.1 m on its axis will be: $({\mu }_0=4\pi \times {10}^{-7}T-m/A)$

1. $1.2\times {10}^{-4}T$
2. $2.4\times {10}^{-4}T$
3. $2.4\times {10}^{4}T$
4. $1.2\times {10}^{4}T$