Questions in Moving Charges and Magnetism

Select	Question
	A current of 2 amp. flows in a long, straight wire of radius 2 mm. The intensity of magnetic field on the axis of the wire is
	The magnetic field at the centre of a circular coil of radius r carrying current $I$ is${B_1}$. The field at the centre of another coil of radius $2r$ carrying same current $I$ is${B_2}$. The ratio $\frac{{{B_1}}}{{{B_2}}}$ is
	1A current flows through an infinitely long straight wire. The magnetic field produced at a point 1 metres away from it is
	Two infinitely long parallel wires carry equal current in same direction. The magnetic field at a mid point in between the two wires is
	A wire in the form of a square of side ‘a’ carries a current i. Then the magnetic induction at the centre of the square wire is (Magnetic permeability of free space = ${\mu _o}$)
	What should be the current in a circular coil of radius $5 cm$ to annul ${B_H} = 5 \times {10^{ - 5}}T$
	A current of 0.1 A circulates around a coil of 100 turns and having a radius equal to 5cm. The magnetic field set up at the centre of the coil is ($\mu_0 = 4\pi \times 10^{–7}$ weber/amp-metre)
	An electron moving in a circular orbit of radius r makes n rotation per second. The magnetic field produced at the centre has a magnitude of
	A long solenoid has n turns per meter and current I Ais flowing through it. The magnetic field at the ends of the solenoid is
	A wire carrying current i is shaped as shown. Section AB is a quarter circle of radius r. The magnetic field is directed