Irodov – Problems in General Physics

(Joyce) #1
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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