21.
The magnetic field at the centre of a current carrying circular loop is B. If the radius of the loop is doubled keeping the current unchanged, the magnetic field at the centre of loop will become:
A
B2
B
B4
C
2B
D
4B
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The magnetic field at the centre of a current carrying circular loop is B. If the radius of the loop is doubled keeping the current unchanged, the magnetic field at the centre of loop will become:
B2
B4
2B
4B
The magnetic field of earth is due to:
induction effect of the sun
the presence of a large magnet at the centre of the earth
interaction of cosmic rays with the current of earth
motion and distribution of some material in an outside the earth
The magnetic field strength due to a short bar magnet directed along its axial line at a distance r is B. What is its value at the same distance along the equatorial line?
B
2B
B2
B4
The magnetic lines of force inside a bar magnet:
do not exist
depends on area of cross-section of bar magnet
are from N-pole to S-pole of the magnet
are from S-pole to N-pole of the magnet.
The Mariner's compass is provided with Gimbals arrangement so as to :
keep the needle always horizontal
give a direct reading of declination
give the direct value of dip
all of the above
The material suitable for making electromagnets should have
high retentivity and high coercivity.
low retentivity and low coercivity.
high retentivity and low coercivity.
low retentivity and high coercivity.
The net magnetic flux through any closed surface, kept in a magnetic field is
zero
μ04π
4πμ0
4μ0π
The neutral point in the magnetic field of a horizontally placed bar magnet is a point where the magnetic field due to that bar magnet is:
zero
more than that of earth
less than that of earth
equal to that of earth
The primary origin of magnetism lies in
atomic current and intrinsic spin of electrons.
polar and non polar nature of molecules.
pauli exclusion principle.
electronegative nature of materials.
The radius of curvature of the path of charged particle in a uniform magnetic file is directly proportional to the
charge on fie particle
Momentum of particle
energy of particle
Strength of field
The relation between geometric length (L) and magnetic length (Lm) is:
Lm = 56 Lg
Lm = 65 Lg
Lm = Lg
Lm = 2RY;UL Lg
The strength of the earthcs magnetic field is
constant everywhere.
zero everywhere.
having very high value.
vary from place to place on the earth's surface.
The vertical component of earth's magnetic field . at a place is sqrt(3) times the horizontal component the value of angle of dip at this place is
30o
45o
60o
90o
Three needles N1 and N3 are made of a ferromagnetic, a paramagnetic and a diamagnetic substance respectively. A magnet, when brought close to them, will
attract N1 strongly, but repel and N3 weakly.
attract all three of them.
attract N1 and strongly but repel N3.
attract N1 strongly, weakly and repel N3 weakly.
What is the angle of dip at a place where the horizontal component of earth's magnetic field is equal to the vertical component?
0o
30o
45o
90o
Which of the following has a low value in ferrites?
Conductivity
Permeability
Magnetic susceptibility
All the above
Which of the following has higher magnetic susceptibility?zdiamagnetic
paramagnetic
ferromagnetic
None of these
Which of the following independent quantities is not used to specify the earth's magnetic field?
Magnetic declination (θ).
Magnetic dip.
Horizontal component of earth's field (BH).
Vertical component of earth's field (BV).
Which of the following is correct about magnetic monopole?
Magnetic monopole exist.
Magnetic monopole does not exist.
Magnetic monopole have constant value of monopole momentum.
The monopole momentum increase due to increase at its distance from the field.
Which of the following is not showing the essential difference between electrostatic shielding by a conducting shell and magnetostatic shielding?
Electrostatic field lines can end on charges and conductors have free charges.
Magnetic field lines can end but conductors cannot end them.
Lines of magentic field cannot end on any material and perfect shielding is not possible.
Shells of high permeability materials can be used to divert lines of magnetic field from the interior region.