The magnetic field along the axis of a circular coil is found to be `[B = (mu_0 Ia^2) / {2(r^2 + a^2)^(3/2)}]` :What is the magnetic field along the axis if r>>a

Give an expression for magnetic field on the axis of a circular current loop. (Expression only).

A shortbar magnet placedin ahorizontal plane has Its axis aligned along the magnetic north-south .direction. Null points are found on the axis of themagnet at 14 cm from the centre of the magnet. The earth’s magnetic field at the place is 0.36 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 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)

A 3.0 cm wire carrying a current of 10 A Is placed inside a solenoid perpendicular to its axis. The magnetic field inside the solenoid is given to be 0.27 T. What is the magnetic force on the wire?