MCQ Questions for Class 12 Medical Physics Magnetism And Matter Quiz 2

$\chi _{1}$ and

$\chi _{2}$ are susceptibilities of a diamagnetic substance at temperatures

$T_{1}K$ and

$T_{2}K$ respectively, then,

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$\chi _{1}T_{1}=\chi _{2}T_{2}$
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$\chi _{1}=\chi _{2}$
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$\chi _{1}\sqrt{T_{1}}=\chi _{2}\sqrt{T_{2}}$
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$\chi _{1}T_{2}=\chi _{2}T_{1}$

Explanation

$\chi_{1}$

$=$

$\chi_{2}$
The magnetic susceptibility of diamagnetic substance is independent of the temperature.

Curie's law states that magnetic susceptibility is

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inversely proportional to the absolute temperature
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exponentially related to temperature
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directly proportional to the absolute temperature
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does not depend on temperature

Explanation

Curie's law states that,magnetic susceptibility is inversely proportional to the absolute temperature.
M

$=$

$\dfrac{CB_{o}}{T}$

$M =$ Magnetic intensity

$\chi$

$=$

$\dfrac{C\mu_{o}}{T}$

$T=$ Absolute temperature

$\chi$

$\alpha$

$\dfrac{1}{T}$

$C=$ Curie constant

The core of electromagnet is made of soft iron, because
a) susceptibility of soft iron is very high
b) coercivity of soft iron is very low

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only a is correct
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only b is correct
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both a and b are correct
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both a and b are wrong

Explanation

Because the suceptibility of the soft iron is very high. and its coercivity is very low,it is very less corrosive.

$\chi$ >> 1 (Because it is a ferromagnetic substance.)

Susceptibility is small and negative for

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para magnetic
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diamagnetic
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ferro magnetic
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electromagnetic

Explanation

diamagnetic

$-1 \leq x < 0$

$\chi =susceptibility$

At Curie temperature, in ferromagnetic materials

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the atomic dipoles get aligned
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the atomic dipoles remains stationary
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the atomic dipoles lose alignment
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magnetism is zero

A magnetic pole of pole strength 9.2 A m. is placed in a field of induction 50x10 $^{-6}$ Tesla. The force experienced by the pole is :

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46N
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46 $\times$ 10 $^{-4}$ N
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4.6 $\times$ 10 $^{-4}$ N
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460N

Explanation

$m=9.2Am$

$B=50\times 10^{-6}T$

$F=B\times m$

$F=9.2\times 50\times 10^{-6}$

$=4.6\times 10^{-4}N$

The magnetic induction at a distance d from the magnetic pole of the unknown strength m is B. If an identical pole is now placed at a distance of 2d from the first pole, the force between the two poles is

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mB
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$\frac{mB}{2}$
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$\frac{mB}{4}$
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2mB

Explanation

$B=\dfrac{\mu _{0}m}{4\pi d^{2}}$

$r=2d$

$F=\dfrac{\mu _{0}m_{1}m_{2}}{4\pi r^{2}}$

$F=\dfrac{\mu _{0}\times m\times m}{4\pi (d)^{2}}$

$F=\dfrac{\mu _{0}m^{2}}{4\pi \times 4d^{2}}$

$F=\dfrac{mB}{4}N$

Two short magnets each of moment $10 A-m^{2}$ are placed in end - on position so that their centres are $0.1\ m$ apart. The force between them is

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$0.4N$
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$0.5N$
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$0.6N$
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$0.8N$

Explanation

Use the formula for force between two magnetic dipoles:

$F=\dfrac{\mu}{4\pi}\dfrac{6M_{1}M_{2}}{d^4}$

$F=0.6 N$

To explain ferromagnetism, we use

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orbital electron hypothesis
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spinning electron hypothesis
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domain theory
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Langevin theory

In the hystersis cycle, the value of H needed to make the intensity of magnetisation zero is called

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retentivity
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coercivity
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Lorentz force
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Pseudo force

Explanation

retentivity, We reduce H to make it zero,whereas B

$\neq$ 0 (standard result of magnetism)

Force between two identical bar magnets whose centres are $r$ meters apart is $4.8 N,$ when their axis are in the same line. If the separation is increased to $2r$ meters, the force between them is reduced to:

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2.4 N
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1.2 N
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0.6 N
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0.3 N

Explanation

$F=\dfrac{\mu _{0}m_{1}m_{2}}{4\pi d^{2}}$

$F\propto \dfrac{1}{d^{2}}$

$Fd^{2}=Constant$

$F_{1}d_{1}^{2}=F_{2}d_{2}^{2}$

$4.8\times r^2=F_{2}(2r)^2$

$F_{2}=1.2 N$

The value of susceptibility for super conductor is

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0
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$\infty$
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+1
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-1

If the magnetic moment of magnet is $0.8 \times 10^{-3}\ Am^{2}$ and the force acting on each pole in a uniform magnetic field strength of $0.48\ gauss$ , is $0.512 \times 10^{-6}N$ . The distance between the poles of the magnet is : (in $cm$ )

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$25$
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$12.5$
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$15$
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$7.5$

Explanation

The relation between Torque and force is

$\tau=\mu*B$

$\tau=F*r$

where r is distance

$F*r=\mu*B$

putting values of

$F=0.512×10^{−6}N,B=0.48 gauss,\mu=0.8×10^{−3} Am^2$

$r=\dfrac{\mu*B}{F}=\dfrac{0.48*0.8×10^{−3} Am^2}{0.512*10^{-6}}=0.075m=7.5cm$

The force acting on a pole of strength of 20 Am is 8x10 $^{-4}$ N, when placed in a magnetic field. The magnetic induction field strength is :

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4 $\times$ 10 $^{-6}$ T
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0.4 $\times$ 10 $^{4}$ T
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4 G
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4 $\times$ 10 $^{-5}$ T

Explanation

$m=20Am$

$F=8\times10^{-4}N$

$F=Bm$

$8\times 10^{-4}=20\times B$

$B=4\times 10^{-5}T$

Two equal poles repel each other with a force of 10 $^{-3}$ N. When placed 2cm apart in air, the pole strength of each is (in amp-m).

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4 $\pi$
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2
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4
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2 $\pi$

Explanation

$F=10^{-3}N$

$d=2cm$

$m_{1}=m_{2}=m$

$F=\dfrac{\mu _{0}m_{1}m_{2}}{4\pi d^{2}}$

$10^{-3} = \dfrac{10^{-7}\times m^{2}}{(2\times 10^{-2})^2}$

$m=2Am$

The purpose of soft iron cylinder between the pole pieces of the horse-shoe magnet in a moving coil galvanometer is

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to increase the magnetic induction in the polar

gap
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to evenly distribute the magnetic lines of force
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to provide a radial magnetic field
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to reduce the magnetic flux leakage in the polar

gap

Complete the following statements with an appropriate word / term to be filled in the blank space(s).

The magnetic lines of force are the lines drawn in a magnetic field along which a _______ pole would move.

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south magnetic
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north magnetic
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north and south magnetic
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north-east

How do bars of bismuth set their length when are placed between the magnetic poles?

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Perpendicular to the lines of force
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Along the lines of force
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Neither perpendicular nor along the lines of force
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In any direction

According to Curie's law, the magnetic susceptibility of a substance at an absolute temperature T is proportional to -

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$1/T$
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$T$
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$1/T$ $^{2}$
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$T$ $^{2}$

Explanation

Curie law

$\chi _{m}\infty \frac{1}{T}$

The SI unit of magnetic field is:

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Tesla
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Weber
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Weber.m
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Gauss

Explanation

The unit of magnetic field is tesla. It is the SI unit of magnetic field. Magnetic field is the measure of magnetic flux (

$\Phi$ ) per unit area.

$1tesla=1wb/m^2$ .

Complete the following statements with an appropriate word / term to be filled in the blank space(s).

Field lines are used to represent a:

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magnetic field
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magnetic force
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magnetic current
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magnetic dipole

Complete the following statements with an appropriate word / term to be filled in the blank space(s).

Field lines are shown closer together where the magnetic field is:

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less
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constant
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greater
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none of these

The force with which a magnet attracts objects like iron is called ....................... .

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Electric Force
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Magnetic Force
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Electromagnetic faoce
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gravitational force

A small piece of a substance is repelled when it is brought near a powerful magnet. What can you say about its type ?

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dimagnetic
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paramagnetic
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ferromagnetic
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non-magnetic

How will the force between the two poles change if the two poles are connected by an iron rod keeping the distance between two magnetic poles constant ?

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Increases
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Decreases
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Remains same
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None of these

State whether true or false.

Magnetic lines of force are primarily curved lines.

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True
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False

Which of the following figures depict non uniform magnetic field?

What is the unit of magnetic flux?

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Dynes
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Oerested
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Gauss
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Weber

Lines of force

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are not imaginary lines
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cannot be mapped on paper
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do not intersect each other
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always intersect each other

Magnetic field lines :

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starts from north pole
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starts from south pole
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starts from current-carrying wires
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are closed loops

The magnetising field required to be applied in opposite direction to reduce residual magnetism to zero is called

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coercivity
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retentivity
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hysteresis
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none of these

A bar magnet has coercivity

$4\times10^3 Am^{-1}$ . It is placed in a solenoid having

$40$ turns per cm and is

$1.2m$ long. The current carried by the solenoid to demagnetize the bar magnet is :

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$6A$
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$8A$
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$5.78A$
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none of these

Explanation

$H=4*10^3A/m$

$B=H*l=4*10^3A/m*1.2=48*10^2A$

$\mu_0=4\pi*10^{-7} Tm/a$

$48*10^2=\mu_o NI=4\pi*10^{-7}*40*I$

$I=\dfrac{48*10^2}{4\pi*10^{-7}*40}=0.095*10^9A$

A magnetic field can be produced by :

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A moving charge
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A changing electric field
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None of these
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Both of these

At Curie temperature the ferromagnetic materials get converted into.

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non-magnetic material.
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para magnetic material.
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dia magnetic material.
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all of the above.

Explanation

Above curie temperature ferromagnetic material behaves like paramganetic materials. There magnetic susceptibilty starts varying linearly with temperature. Their

$I$ becomes too small above curies temperature.

Therefore, nature of ferrromagnetic materials becomes paramagnetic.

Figure shows a some of the equipotential surface of the magnetic scalar potential. The magnetic field at a point in the region is :

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$2\times10^{-5}T$
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$10^{-5}T$
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$10^{-4}T$
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$2\times10^{-4}T$

Explanation

Magnetic field

$\displaystyle B=-\frac{dV_B}{dx}=-\frac{\Delta V_B}{\Delta x}$
Where

$x$ is the distance in the perpendicular direction on magnetic field

$\displaystyle B =\dfrac{2\times10^{-5}-1\times10^{-5}}{(0.1)\sin30}=2\times10^{-4}T$ .

A powerful magnet attracts

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all materials.
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only ferromagnetic materials and their ores.
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some materials and repels some other materials.
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only iron and its ores but does not repel any material.

Which of the following are best suited to make the core of a transformer?

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soft iron
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steel
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alnico
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none of these

The value of Curie temperature for

$Ni$ is nearly

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$631K$
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$770K$
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$890K$
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$1100K$

Explanation

Above

$631 K \ Ni$ behaves like paramagnetic material.

Two magnetic lines of force:

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never cut each other
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cut near the poles
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cut according to the position of the magnet
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cut at neutral points

A current carrying wire in the neighbourhood produces -

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No field
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Electric field only
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Magnetic field only
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Electric and magnetic fields

Which of the following cannot be ferromagnetic?

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alloys
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solids
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liquids
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gases

If a diamagetic solution is poured into a U-tube and one arm of this U-tube is placed between the poles of a strong magnet, with the meniscus in line with the field, then the level of solution will :

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rise
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fall
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oscillate slowly
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remain as such

What is the direction of magnetic field at the centre of a coil carrying clockwise current ?

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No direction
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normal to the axis of coil inwards.
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Along the axis of coil inwards.
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Along the axis of coil outwards.

The space around a magnet where its influence can be detected is called ..............

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curve
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magnetic field
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magnetic needle
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horse shoe

The magnetic lines of force around a very weak magnet are :

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overlapping each other
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parallel lines
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not close continuous curves
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close continuous curves

Which of the following is/are true for "magnetic lines of force around a bar magnet"?

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are closed continuous curves
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travel from north to south outside the magnet
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bend around the length of magnet
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all the above

A straight wire lying in a horizontal plane carries a current from north to south. What will be the direction of magnetic field at a point just underneath it?

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Towards north.
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Towards east.
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Towards west.
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Towards south.

Magnetic lines of force can pass through:

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only magnetic substances
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only non-magnetic substances
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both (a) and (b)
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none of the above

Magnetic lines do not intersect one-another because:

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they are at a distance
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they are in the same direction
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they are parallel to one another
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in the point of intersection there will be two direction of the magnetic field, which is impossible

The strength of magnetic field around a bar magnet :

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decrease with the decrease in distance from the magnet
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decrease with the increase in distance from the magnet
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remain constant with increase in distance from magnet
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becomes zero with decrease in distance from magnet

CBSE Questions for Class 12 Medical Physics Magnetism And Matter Quiz 2 - MCQExams.com

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Practice Class 12 Medical Physics Quiz Questions and Answers

CBSE Questions for Class 12 Medical Physics Magnetism And Matter Quiz 2 - MCQExams.com

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Practice Class 12 Medical Physics Quiz Questions and Answers

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