If the angle of dip at two places are 30° and 45° respectively, then the ratio of horizontal components of the earth’s magnetic field at the two places will be
A steel wire of length l has a magnetic moment M .It is then bent into a semicircular arc. The new magnetic moment is
a) M
b) 2M/π
c) M/l
d) Ml
A current loop placed in a magnetic field behaves like a
a) Magnetic substance
b) Magnetic pole
c) Magnetic dipole
d) all true
Unit of magnetic dipole moment is
a) ampere meter
b) ampere/meter⁻¹
c) ampere metre²
d) ampere/metre²
A bar magnet of dipole moment ’m’ cut into two equal pieces transverse to its length. Dipole moment of each part is
a) Remain same
b) m/2
c) 2m
d) none of the above
A current carrying small loop behaves like a small magnet. If A be its area and M its magnetic moment, the current in the loop will be
a) M/A
b) A/M
c) MA
d) A²M
In double –slit experiment the distance of the second dark fringe from the central line is 3 mm. The distance of the fourth bright fringe from the central line is
(A) 6 mm
(B) 8mm
(C) 12 mm
(D) 16 mm
Which field is more effective in electromagnetic waves?
(A) Electric field
(B) magnetic field
(C) both electric and magnetic field
(D) none of these
To observe diffraction, the size of the obstacle
(a) should be X/2, where X is the wavelength.
(b) should be of the order of wavelength.
(c) has no relation to wavelength.
(d) should be much larger than the wavelength.
Two sources of intensity I and 4I are used in an interference experiment . Find the intensity at points where waves from two sources superimpose with phase difference π/2 is
I. 4I
II. 6I
III. 5I
IV. 9I
The coil of a moving coil galvanometer is wound over a metal frame in order to-
(a) reduce hysteresis
(b) increase sensitivity
(c) increase moment of inertia
(d) provide electromagnetic damping.
When a body charges by conduction, its mass
(A) Remains same
(B) Increases
(C)Decreases
(D)Increase or decrease
Which of the following is not a property of electric field lines?
(A) Field lines are closed and continuous curves without any breaks.
(B) Two field lines cannot cross each other.
(C) Field lines start at positive charges and end at negative charges.
(D) They do not form closed loops.