Magnetic Moment

Q.

What is meant by the neutral point of the magnetic field?

Q. Two short bar magnets each of magnetic moment $M$ are placed as shown in the figure. The magnetic field at the point $P$ will be

1. $\frac{{\mu }_0}{4\pi }\frac{2\sqrt{2}M}{d^3}$ towards right
2. $\frac{{\mu }_0}{4\pi }\frac{2\sqrt{2}M}{d^3}$ towards left
3. $\frac{{\mu }_0}{4\pi }\frac{2M}{d^3}$ towards right
4. $\frac{{\mu }_0}{4\pi }\frac{2M}{d^3}$ towards left

Q. The magnetic moment of a magnet of length 10 cm and pole strength 4.0 Am will be

1. $0.4A{m}^2$
2. $1.6A{m}^2$
3. $20A{m}^2$
4. $8.0A{m}^2$

Q. A very small magnet is placed in the magnetic meridian with its south pole pointing north. The null point is obtained 20 cm away from the centre of the magnet. If the earth's magnetic field (horizontal component) at this point be 0.3 gauss, the magnetic moment of the magnet i

1. $8.0\times {10}^{2}e.m.u$
2. $1.2\times {10}^{3}e.m.u$
3. $2.4\times {10}^{3}e.m.u$
4. $3.6\times {10}^{3}e.m.u$

Q. The effective length of a magnet is 31.4 cm and its pole strength is 0.5 Am. The magnetic moment, if it is bent in the form of a semicircle will be

1. $0.1A{m}^2$
2. $0.01A{m}^2$
3. $0.2A{m}^2$
4. $1.2A{m}^2$