An iron ring of relative permability `mu_r` has windings of insulated copper of wire of n tunrs per metre. When the current in the windings is I, find the expression for the magnetic field in the ring.

Figure shows a right-angled isosceles DeltaPQR having its base equal to a. A current of I ampere is passing downwards along a thin straight wire cutting the plane of paper normally as shown at Q. Likewise a similar wire carries an equal current passing normally upwards at R. Find the magnitude and direction of the magnetic field induction B at P. Assume the wires to be infinity long.

A Rowland ring of mean radius 15 cm has 3500 turns of wire wound on a ferromagnetic core of relative permeability 800. What is the magnetic field B in the core for a magnetising current of 1.2 A?

A wire loop is formed by joining two semicircular wires of radii r_1 and r_2 as shown in the figure . The loop carries a current I, find the magnetic field at the centre O.

A metallic wire carrying a current I is bent into the form as shown in the figure. The circular portion ABC of the wire is of radius r and the straight portion AC subtends an angle 2theta at the centre O. Find the magnetic field due to the conductor at point O. If the radius of the curved path is r, find the magnetic field at the centre O.

What does a toroid consist of ? Find out the expression for the magnetic field inside a toriod for N turns of the coil having an average radius r and carrying current I. show that the magnetic field in the open space inside and outside the torroid is zero.

Two identical circular wires P and Q each of radius R and carrying current 'I' are kept in perpendicular planes such that they have a common centre as shown in the figure. Find the magnitude and direction of the net magnetic field at the common centre of the two coils.

A steel wire of mass mu per unit length with a circular cross section has a radius of 0.1 cm. The wire is of length 10 m when measured lying horizontal, and hangs from a hook on the wall. A mass of 25 kg is hung from the free end of the wire. Assuming the wire to be uniform and lateral strains < < longitudinal strains, find the extension in the length of the wire. The density of steel is 7860 kg m^-3 (Young's modulues Y = 2 xx 10^11 N m^-2)

A small retangular coil ABCD contains 140 turns of wire. The sides AB and BC of the coil are of length 4.5 and 2.8 cm respectively, as shown in the figure The coil is held between the poles of a large magnet so that the coil can rotate about an axis thorugh its centre. The magnet produces a uniform magnetic field of flux density B between its poles. When the current in the coil is 170 mA, the maximum torque produced in the coil is 2.1 xx 10^-3 N m . For the coil in the position shown in the figure. calculate the magnitude of the force on (i) side AB of the coil and (ii) side BC of the coil.

For a circular coil of radius R and N turns carrying current I, the magnitude of the magnetic field at a point on its axis at a distance x from its centre is given by, B= (mu_0IR^2N)/(2(x^2+R^2)^(3/2)) . Consider two parallel co-axial circular coils of equal radius R, and number of turns N, carrying equal currents in the same direction, and separated by a distance R. Show that the field on the axis around the mid-point between the coils is uniform over a distance that is small as compared to R, and is given by, B=0.72 (mu_0NI)/R approximately.

A Rowland ring has 10^3 turns per uit length. On passing a current of 2 A, magnetic induction is measured to be 1.5 Wb m^-2 . Calculate magnetising field intensity.