Irodov – Problems in General Physics

Fig. 3.74.

of the loop is equal to pm. Find the magnitude and direction of the

force vector applied to the loop if the vector pm

(a) is parallel to the straight conductor;

(b) is oriented along the radius vector r;

(c) coincides in direction with the magnetic field produced by the

current I at the point where the loop is located.

3.270. A small current-carrying coil having a magnetic moment

pm is located at the axis of a round loop of radius R with current I

flowing through it. Find the magnitude of the vector force applied

to the coil if its distance from the centre of the loop is equal to x

and the vector pm, coincides in direction with the axis of the loop.

3.271. Find the interaction force of two coils with magnetic mo-

ments Thin = 4.0 mA• m 2 and p 2 ,, = 6.0 mA• m 2 and collinear axes if

the separation between the coils is equal to 1 = 20 cm which exceeds

considerably their linear dimensions.

3.272. A permanent magnet has the shape of a sufficiently thin

disc magnetized along its axis. The radius of the disc is R = 1.0 cm.

Evaluate the magnitude of a molecular current I' flowing along the

rim of the disc if the magnetic induction at the point on the axis of

the disc, lying at a distance x = 10 cm from its centre, is equal to

B = 30 RT.

3.273. The magnetic induction in vacuum at a plane surface of

a uniform isotropic magnetic is equal to B, the vector B forming an

angle a with the normal of the surface. The permeability of the magnet-

ic is equal to Find the magnitude of the magnetic induction B' in

the magnetic in the vicinity of its surface.

3.274. The magnetic induction in vacuum at a plane surface of

a magnetic is equal to B and the vector B forms an angle 0 with the

normal n of the surface (Fig. 3.74). The permeability of the magnetic

is equal to R. Find:

(a) the flux of the vector H through the spherical surface S of

radius R, whose centre lies on the surface of the magnetic;

(b) the circulation of the vector B around the square path 1' with

side 1 located as shown in the figure.

3.275. A direct current I flows in a long round uniform cylindrical

wire made of paramagnetic with susceptibility x. Find:

(a) the surface molecular current is;

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