MODEL QUESTIONS (IPE PATTERN)

A coil of $20$ turns has an area of $800 {\mathrm{mm}}^2$ and carries a current of $0.5 \mathrm{A}$. If it is placed in a magnetic field of intensity $0.3 \mathrm{T}$ with its plane parallel to the field, what is the torque that it experiences?

In the Bohr atom model the electrons move around the nucleus in circular orbits. Obtain an expression the magnetic moment $\mu$ of the electron in a hydrogen atom in terms of its angular momentum $L$.

A solenoid of length $22.5 \mathrm{cm}$ has a total of $900$ turns and carries a current of $0.8 \mathrm{A}$. What is the magnetising field $H$(in $\mathrm{A} {\mathrm{m}}^{-1}$) near the centre of solenoid?

A bar magnet of length $0.1 \mathrm{m}$ and with a magnetic moment of $5 {\mathrm{Am}}^2$ is placed in a uniform magnetic field of intensity $0.4 \mathrm{T}$, with its axis making an angle of $60°$ with the field. What is the torque on the magnet?

If the Earth's magnetic field at the equator is about $4\times {10}^{-5 }\mathrm{T}$, what is its approximate magnetic dipole moment? (radius of earth $=6400 \mathrm{km}$)

The horizontal component of the Earth's magnetic field at a certain place is $2.6\times {10}^{-5} \mathrm{T}$ and the angle of dip is $60°$. What is the magnetic field of the earth at this location?

A solenoid of insulated wire is wound on a core with relative permeability $400$. If the number of turns per metre is $1000$ and the solenoid carries a current of $2 \mathrm{A}$, calculate $H, B$ and magnetisation $M$.

A short bar magnet placed in a horizontal plane has its axis aligned along the magnetic north-south direction. Null points are found on the axis of the magnet at $14 \mathrm{cm}$ from the centre of the magnet. The earth's magnetic field at the place is $0.36 \mathrm{G}$ and the angle of dip is zero. What is the total magnetic field on the normal bisector of the magnet at the same distance as the null-point(i.e., $14 \mathrm{cm}$) from the centre of the magnet? (At null points, field due to a magnet is equal and opposite to the horizontal component of earth's magnetic field.)