Moving Charges and Magnetism

A conducting wire is in the shape of a regular hexagon which is inscribed inside an imaginary circle of radius $R$. If a current $I$ flows the wire, the magnitude of magnetic field at the centre of the circle is

A coil having 100 turns is wound tightly in the form of a spiral with inner and outer radii 1 cm and 2 cm , respectively. When a current 1 A passes through the coil, the magnetic field at the centre of the coil is

An infinite long wire lying along the $Y$-axis, is carrying a current $I$ as shown in the figure. The magnetic flux through a circular loop of radius $R$ in the $x y$-plane is [assume, $\mu_0=$ magnetic in free space permeability]

The ratio of the magnetic field inside a solenoid at an axial point well inside and at an axial end point is

A straight wire of mass 0.2 kg and length 1.5 m carries a current 2A is shown in the figure. It is suspended in mid-air by a uniform magnetic field $B$ pointing to the plane of paper. The magnitude of magnetic field is (ignore, earth's magn...

A 50 cm long solenoid has winding of 400 turns. What current must pass through it to produce a magnetic field of induction $4 \pi \times 10^{-3} \mathrm{~T}$ at the centre?

A circular coil of 10 turns and radius 10 cm is placed in a uniform magnetic field of 0.1 T normal to the plane of the coil. If the current in the coil is 5 A , then the magnitude of the torque on the coil is

Two tangent galvanometers $A$ and $B$ have coils of radii 8 cm and 16 cm respectively and having resistance of 8 $\Omega$ each. They are connected in parallel with a cell of emf 4 V and negligible internal resistance. The deflections produc...

A particle of charge $q$ and mass $m$ moves in a circular orbit of radius $r$ with angular speed $\omega$. The ratio of the magnitude of its magnetic moment to that of its angular momentum is