Question Bank for 12th Class Physics Magnetism Case Based (MCQs) - Magnetism and Matter

The earth's magnetic field at a point on its suface is usually characterised by three quantities : [a] declination [b] inclination or dip and [c] horizontal component of the field. These are knwon as the elements of the earth's magnetic field. At a place, angle between geographic meridian and magnetic meridian is defined as magnetic declination, whereas angle made by the earth's magnetic field with the horizontal in magnetic meridian is known as magnetic dip.

In a certain place, the horizontal component of magnetic field is \[\frac{1}{\sqrt{3}}\] times the vertical component. The angle of dip at this place is

A)

zero

B)

\[\pi /3\]

C)

\[\pi /2\]

D)

\[\pi /6\]

View Solution

2)

The angle betwen the true geographic north and the north shown by a compass needle is called as

A)

inclination

B)

magnetic declination

C)

angle of meridian

D)

magnetic pole.

View Solution

3)

The angles of dip at the poles and the equator respectively are

A)

\[30{}^\circ ,\text{ }60{}^\circ \]

B)

\[0{}^\circ ,\text{ }90{}^\circ \]

C)

\[45{}^\circ ,\text{ }90{}^\circ \]

D)

\[90{}^\circ ,\text{ }0{}^\circ \]

View Solution

4)

A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It

A)

will become rigid showing no movement

B)

will stay in any position

C)

will stay in north-south direction only

D)

will stay in east-west direction only.

View Solution

5)

Select the correct statement from the following

A)

The magnetic dip is zero at the centre of the earth

B)

Magnetic dip decreases as we move away from the equator towards the magnetic pole

C)

Magnetic dip increases as we move away from the equator towards the magnetic pole

D)

Magnetic dip does not vary from place to place.

View Solution

6)

Directions : (6-10)

Gausss Low for Magnetism

By analogy to Guass's law of electrostatics, we can

write Gauss's law of magnetism as \[\oint{\overrightarrow{B}\,.\,\overrightarrow{ds}}={{\mu }_{0}}{{m}_{inside}}\] wehre \[\oint{\overrightarrow{B}\,.\,\overrightarrow{ds}}\] is the magnetic flux and \[{{m}_{inside}}\]is the net pole strength inside the closed surface.

We do not have an isolated magnetic pole in nature. At least none has been found to exist till date. The smallest unit of the source of magnetic field is a magnetic dipole where the net magnetic pole is zero. Hence, the net magnetic pole enclosed by any closed surface is always zero. Correspondingly, the flux of the magnetic field through any closed surface is zero.

Consider the two idealised systems

(i) a parallel plate capacitor with large plates and small separation and

(ii) a long solenoid of length L > > R, radius of cross-section

In (i) \[\overrightarrow{E}\] is ideally treated as a constant betwen plates and zero outside. In (ii) magnetic field is constant inside the solenoid and zero ouside. These idealised assumption, however, contradict fundamental laws as

A)

case (i) contradicts Gauss's law for electrostatic field

B)

case (ii) contradicts Gauss's law for magnetic fields

C)

case (i) agrees with \[\oint{\overrightarrow{E}\,.\,\overrightarrow{dl}}=0\]

D)

case (ii) contradicts \[\oint{\overrightarrow{H}\,.\,\overrightarrow{dl}}={{I}_{en}}\]

View Solution

7)

The net magnetic flux through any closed surface, kept in a magnetic field is

A)

zero

B)

\[\frac{{{\mu }_{0}}}{4\pi }\]

C)

\[4\pi {{\mu }_{0}}\]

D)

\[\frac{4{{\mu }_{0}}}{\pi }\]

View Solution

8)

A closed surface S encloses a magnetic diple of magnetic moment 2ml. The magnetic flux emerging from the surface is

A)

\[{{\mu }_{0}}m\]

B)

zero

C)

\[4H\,{{\mu }_{0}}m\]

D)

\[\frac{2\,m}{{{\mu }_{0}}}\]

View Solution

9)

Which of the following is not a consequence of Gauss's law?

A)

The magnetic poles always exist as unlike pairs of equal strength

B)

If several magnetic lines of forces enter in a closed surface, then an equal number of lines of force must leave that surface

C)

There are abundant sources or sinks of the magnetic field inside a closed surface.

D)

Isolated magnetic poles do not exist.

View Solution

10)

The surface integral of a magnetic field over a surface

A)

is proportional to mass enclosed

B)

is proportional to charge enclosed

C)

is zero

D)

equal to its magnetic flux through that surface.

View Solution

11)

Directions : (11-15)

Magnetisation and Magnetic Intensity

When the atomic dipoles are aligned partially or fully, there is a net magnetic moment in the direction of the field in any small volume of the material. The actual magnetic field inside material placed in magnetic field is the sum of the applied magnetic field and the magnetic field due to magnetisation. This field is called magnetic internsity (H)

\[H=\frac{B}{{{\mu }_{0}}}-M\]

where M is the magnetisation of the material, \[{{\mu }_{0}}\]is the permittivity of vacuum and B is the total magnetic field. The measure that tells us how a magnetic material responds to an external field is given by a dimensionless quantity is appropriately called the magnetic susceptibility : for a certain class of magnetic materials, intensity of magnetisation is directly proportional to the magnetic intensity

Magntisation of a sample is

A)

volume of sample per unit magnetic moment

B)

net magnetic moment per unit volume

C)

ratio of magnetic moment and pole strength

D)

ratio of pole strength to magnetic moment.

View Solution

12)

Identify the wrongly matched quantity and unit pair

A)

Pole strength - Am

B)

Magnetic - dimensionless Susceptibility number

C)

Intensity of - \[A{{m}^{-1}}\] Magnetization

D)

Magnetic permeability - Henery m

View Solution

13)

A bar magnet has length 3 cm, cross-sectional area \[2\,c{{m}^{2}}\] and magnetic moment \[3\,A\,{{m}^{2}}\]. The intensity of magnetisation of bar magnet is

A)

\[2\times {{10}^{5}}\,\,A/m\]

B)

\[3\times {{10}^{5}}\,\,A/m\]

C)

\[4\times {{10}^{5}}\,\,A/m\]

D)

\[5\times {{10}^{5}}\,\,A/m\]

View Solution

14)

A solenoid has core of a material with relative permeability 500 and its windings carry a current of 1 A. The number of turns of the solenoid is 500 per metre. The magnetization of the material is nearly

A)

\[2\centerdot 5\times {{10}^{3}}A{{m}^{-1}}\]

B)

\[2\centerdot 5\times {{10}^{5}}A{{m}^{-1}}\]

C)

\[2\centerdot 0\times {{10}^{3}}A{{m}^{-1}}\]

D)

\[2\centerdot 0\times {{10}^{5}}A{{m}^{-1}}\]

View Solution

15)

The relative permeability of iron is 6000. Its magnetic susceptibility is

A)

5999

B)

60001

C)

\[6000\times {{10}^{-7}}\]

D)

\[600\times {{10}^{7}}\]

View Solution

16)

Directions : (16-20)

Earths Magnetic field

The magnetic field lines of the earth resemble that of a hypothetical magnetic dipole located at the centre of the earth. The axis of the dipole is presently tilted by approximately \[11\centerdot 3{}^\circ \] with respect to the axis of rotation of the earth.

The pole near the geographic North pole of the earth is called the North magnetic pole and the pole near the geographic South pole is called South magnetic pole.

The strength of the earth's magnetic field varies from place to pake on the earth's surface, its value being of the order of

A)

\[{{10}^{5}}T\]

B)

\[{{10}^{-6}}\,T\]

C)

\[{{10}^{-5}}\,T\]

D)

\[{{10}^{8}}\,T\]

View Solution

17)

A bar magnet is placed North-south with its North-pole due North. The points of zero magnetic field will be in which direction from centre of magnet?

A)

North-South

B)

East-West

C)

North-East and South-West

D)

None of these.

View Solution

18)

The value of angle of dip is zero at the magnetic equator because on it

A)

V and H are equal

B)

the values of V and H zero

C)

the value of V is zero

D)

the value of H is zero.

View Solution

19)

The angle of dip at a certain place, where the horizontal and vertical components of the earth's magnetic field are equal, is

A)

\[30{}^\circ \]

B)

\[90{}^\circ \]

C)

\[60{}^\circ \]

D)

\[45{}^\circ \]

View Solution

20)

At a place, angle of dip is \[30{}^\circ \]. If horizontal component of earth's magnetic field is H. then the total intensity of magnetic field will be

A)

\[\frac{H}{2}\]

B)

\[\frac{2H}{\sqrt{3}}\]

C)

\[H\sqrt{\frac{3}{2}}\]

D)

2H

View Solution

21)

Directions : (21-25)

Magnetic field due to a Hollow Wire

The field of a hollow wire with constant current is homogeneous.

Curves in the graph shown give, as ruction of radial distance r, the magnitude B of the magnetic field inside and outside four long wires a, b, c and d carrying currents that are uniformly distributed across the cross sections of the wires. Overlapping portions of the plotsare indicated by double labels.

Which wire has the greatest magnitude of the magnetic field on the surface?

A)

a

B)

b

C)

c

D)

d

View Solution

22)

The current density in a wire a is

A)

greater than in wire c

B)

less than in wire c

C)

equal to that in wire c

D)

not comparable to that of in wire c doc to tack of information

View Solution

23)

Which wire has the greatest radius ?

A)

a

B)

b

C)

c

D)

d

View Solution

24)

A direct current I flows along the length of an infinitely long straight thin walled pipe, then the magnetic field is

A)

uniform throughout the pipe but not zero

B)

zero only along the axis of the pipe

C)

zero at any point inside the pipe

D)

maximum at the centre and minimum at he edges.

View Solution

25)

In a coaxial, straight cable, the central conductor and the outer conductor carry equal currents in opposite direction. The magnetic field is zero

A)

outside the cable

B)

inside the inner conductor

C)

inside the outer conductor

D)

in between the two conductors.

View Solution

12th Class Physics Magnetism Question Bank

done Case Based (MCQs) - Magnetism and Matter Total Questions - 25

Study Package

Case Based (MCQs) - Magnetism and Matter

Case Based (MCQs) - Magnetism and Matter Total Questions - 25