How will the magnetic field intensity at the centre of a circular coil carrying current change if the current through the coil is doubled and the radius of the coil is halved?

Which one of the following will experience maximum force when projected with the same velocity $V$ perpendicular to the magnetic field $B$.(i) $\alpha -$particle and (ii) $\beta -$particle.

Which one of the following will experience maximum force when projected with the same velocity $V$ perpendicular to the magnetic field $B$.(i) $\alpha -$particle and (ii) $\beta -$particle.

An ammeter and a milliammeter are converted from the same galvanometer. Out of the two which current measuring instrument has a higher resistance?

A current is set up in a copper pipe. Is there a magnetic field inside the pipe.