Along the direction of current carrying wire, the value of magnetic field is ?

Two circular coils made of similar wires but of radius 20 cm and 40 cm are connected in parallel. The ratio of magnetic fields at their centre is -

An ionized gas contains both positive and negative ions. If it is subjected simultaneously to an electric field along the +x direction and a magnetic field along the +z direction, then-

A coil having N turns is wound tightly in the form of a spiral with inner and outer radii a and b respectively. When a current I passes through the coil, the magnetic field at the centre is-

A charged particle enters a uniform magnetic field with a velocity vector at an angle of 45° with the magnetic field. The pitch of helical path followed by the particle is p. The radius of the helix will be -

A rectangular loop of metallic wire is of length a and breadth b and carries a current i. The magnetic field at the centre of the loop is -

A circular coil carrying current I is placed in a region of uniform magnetic field acting perpendicular to a coil as shown in the figure. Mark correct option.

The value of intensity of magnetic field at a point due to a current carrying conductor depends -