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) M
b) 2M/π
c) M/l
d) Ml
b) 2M/π
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 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
Magnetic field lines form continuous closed loops
a) magnet is always a dipole
b) magnet is always a monopole
c) magnetic material is permeable
d) none of the above
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
What happens if one of the slits, say S1 in Young’s double , slit experiment-is covered with a glass plate which absorbs half the intensity of light from it?
(a) The bright fringes become less-bright and the dark fringes have a finite light intensity
(b) The bright fringes become brighter and the dark fringes become darker
(c) The fringe width decreases
(d) No fringes will be observed
The angle of incidence at which reflected light is totally polarised for reflection from air to glass (refractive index n) is
In a purely resistive a.c. circuit, the current
(a) is in phase with the e.m.f.
(b) leads the e.m.f. by a difference of π radians phase
(c) leads the e.m.f. by a phase difference of π/2 radians
(d) lags behind the e.m.f. by a phase difference of π/4 radians
A long solenoid has 2000 turns. When a current of 2 A flows through it, then the magnetic flux linked with each turn of the solenoid is 2 × 10⁻³ Wb. The self inductance of the solenoid is
(a) 1 H
(b) 2 H
(c) 3 H
(d) 4 H
If the width of the slit in single slit diffraction experiment is doubled, then the central maximum of diffraction pattern becomes:
(A) broader and brighter
(B) broader and fainter
(C) sharper and fainter
(D) sharper and brighter
The force between two charges, when placed in free space, is 5N. if they are in a medium of relative permittivity 5, the force between them will be
A. 1N
B. 25N
C. 2.5N
D. 1/5N