A uniform electric field and a uniform magnetic field are produced, pointed in the same direction. An electron is projected with its velocity pointed in the same direction :

An electron moving with a speed u along the positive x-axis at y = 0 enters in a region of
uniform magnetic field \[\overrightarrow{B}=-B_{0}\hat{k}\] which exists to
the right of y-axis. The electron exits from the region after some time with speed v at coordinate
y, then :

A cube made of wires of equal length is connected to a battery as shown in the figure. The magnetic field at the centre of the cube is :

Adjoining figure shows a rectangular loop of conductor carrying a current i. The length and breadth of the loop are respectively a and b. The magnetic field at the centre of loop is :

Two long parallel wires are at a distance 2d apart. The carry steady equal current flowing out of the plane of the paper as shown. The variation of the magnetic field along the line XX’ is given by :

A length of wire carries a steady current. It is bent first to form a circular plane coil of one turn. The same length is now bent more sharply to give a double loop of smaller radius. The magnetic field at the centre caused by the same current is :

A coil having N turns is would 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 its centre is :

A particle carrying a charge equal to 100 times the charge on an electron is rotating per second in a circular path of radius 0.8m. The value of the magnetic field produced at the centre will be : (μ0 = permeability constant)

The magnetic induction at the centre O of the current carrying bent wire shown in the adjoining figure is :

A cell is connected between the points A and C of a circular conductor ABCD with O as centre and angle AOC = 60°. If B1 and B2 are the magnitudes of the magnetic fields at O due to the currents in ABC and ADC respectively, then ratio B1/B2 is :-