Question

15. Give an expression for time period of oscillation when a magnetic needle placed in uniform magnetic
field.
16. (a) Define magnetic declination?
(b) Define magnetic dip or inclination.
17. When is the flux through a surface
(a) Maximum?
(b) Zero?
18. Write any two applications of eddy currents.
19. Dive any two uses of microwaves.​

Answer 1

15.) A small compass magnetic needle of magnetic moment m and moment of inertia I is made to oscillate in the magnetic field, B. Time period of oscillation is given by T = 2π Im.

16.) (a) Magnetic declination, sometimes called magnetic variation, is the angle between magnetic north and true north. Declination is positive east of true north and negative when west.

(b) The angle made between the total of earth's magnetic field (Be) with the surface of the earth (horizontal component) in the magnetic meridian is known as angle of dip. The yellow lines indicate the surface of the earth. ... This angle of dip is 90 degrees at the equator and 0 degrees at the poles.

17.) The magnetic flux through an area element is (i) maximum when the magnetic induction is the direction of the area vector, and (ii) Zero when the magnetic induction is perpendicular to the area vector.

18.) Mention any two applications of eddy currents.

Induction furnace (heating effect of eddy current)

Dead-beat galvanometer (electromagnetic damping)

Electric brakes, induction motors.

19.) Microwaves are widely used in modern technology, for example in point-to-point communication links, wireless networks, microwave radio relay networks, radar, satellite and spacecraft communication, medical diathermy and cancer treatment, remote sensing, radio astronomy, particle accelerators, spectroscopy, industrial .

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