Electricity and Magnetism Answers

Metallic iron contains approximately 1029 atoms per cubic meter. The magnetic moment of each iron atom is 1.8 × 10−23 Am−1. If all the dipoles were perfectly aligned what would be the magnetisation M and the magnetic moment of a bar 10 cm long and 1cm2 in cross-section?

An electron and a proton, having the same kinetic energy, enter a region of uniform magnetic field moving perpendicular to the field. Calculate the ratio of the radii of their circular paths in the field.

Two long, straight, parallel wires 24 cm apart carry currents of I1 = 30A andI2 = 20A in the same direction. Determine the magnetic field in the plane of the twowires at a point halfway between the wires.

Twolargeparallelconductingplatescarryingequalandoppositechargesontheir surfaces facing each other are placed at a distance of 0.75 m. An electron placed at some point between the plates experiences an electrostatic force of 4.8 × 10-16 N. Calculate the magnitude of the electric field at the position of the electron between the plates. Also determine the potential difference between the plates.

A positron of mass m moving with speed Vo enters into a region of uniform magnetic field B ,(produce out of the plane of paper) . The width of the region of magnetic field is " (3mVo)/(2eB)". Find the time spent by the particle in magnetic field if "theta" is nearly 90°.
(a) (2πm)/(3Be). (b). (3πm)/2Be
(c) (2πm)/eB. (d). Infinite

Show that for two scalar fields f and g:
∇.[∇f ×( f ∇g)]= 0

a) Three charges q, 2q and q are to be placed on a straight wire of length 10 m.
Determine the positions where the charges should be placed so that the electrostatic potential energy of the system is a minimum.

the Three charges q, 2q and q are

Three charges q, 2q and q are to be placed on a straight wire of length 10 m.
Determine the positions where the charges should to be placed so that the
electrostatic potential energy of the system is a minimum.

The volume charge density of a solid sphere of radius 0.75 m is 0.25 nCm−3 . Apply Gauss’s law to calculate the
a) electric flux through the sphere and
b) electric field at a distance of 1.5 m and at a distance of 0.50 m from the centre of the sphere, respectively. If this sphere were made of conducting material, what would the values of the electric fields be at these distances?