01․ Find H for centre of solenoid having finite length d = 1 unit where N = no of turns = 500, I = 2 A.
From Biot Savarts law, magnetic field intensity for a solenoid is given as H = NI/ux.
02․ A magnetic vector potential is given by the expression A = (- cos x) (cos y) uz. The flux density at the origin is
B = curl of A Since flux density at origin (x = 0, y = 0) so B = 0.
03․ A circular loop has its radius increasing at a rate of 2 m/s. The loop placed perpendicular to a constant magnetic field of 0.5 wb/m2. When the radius of the loop is 4 m. the emf induced in the will be
Area of the loop A = π r2 Magnetic of unit emf induced dQ/dt.
04․ A magnetic field B = 5 × 10-2 uz T exerts a force on 0.02 m conductor along the x-axis. The conductor carried a current of 5 mA in the – ux direction. What force must be applied to the conductor to hold it in position
F = IL × B Applied forced Fa = - (IL × B) Since Fa force hold conductor position. So the force will be opposed.
05․ The hysteresis loop of a magnetic material has an area of 5 cm2 with the scale given as 1 cm = 2 AT and 1 cm = 50 mwb At 50 Hz; the total hysteresis loss is
Power loss in watt given as, Ph = W h v.f Where Wh = energy density loss V = Volume of material In this case, Wh.V = area of hysteresis loop = 5 cm2.
06․ A wire 1 m long carries a current of 5A and is at an angle of 30o with B = 1.5 wb/m2. Magnitude of force is
F = BIL sinθ.
07․ A negative point charge q = - 40 nC is moving with velocity of 6 × 106 m/s in a direction specited by unit vector uy + 0.6 uz. Find the magnitude of force vector on the moving particle by the field B = 2 ux + 3 uy + 5 uz mT and E = 2 ux - 3 uy + 5 uz KV/m
Apply F = Q(E + V × B).
08․ The Kirchhoff’s current law is implict in expression
Current at a node is zero, current entering = current leaving. So, surface integral of (j.ds) = 0.
09․ The magnetic field at any point on the axis of current carrying circular coil will be
With coil x – y plane, the field will be in uz direction.
10․ A coil of 300 turns is wound on a non magnetic core having a mean circumference of 300 mm and a cross sectional area of 300 mm2. The inductance of the coil corresponding to a magnetizing current of 6 A will be
Inductance of coil,