The B - H Curve of a ferromagnetic material is as shown in figure: b Identify the value of retentivity and coercivity from the figure.

Retentively is the ability of a material to resist or to retain magnetic field, and it’s measured by the total strength of a magnetic field that is left in a material when an inducing field is removed from the material. The units in which retentively of a material is measured is Weber per square meter or Weber - 2 . In this digram Ob represents retentively Coercivity is a measurement of a ferromagnetic substance's ability to withstand an external magnetic field without getting demagnetized. The units in which coercivity is measured is ampere per meter and denoted as overset. It’s also known as coercive force or coercive field. In this digram Oc represents Coercivity.

∮ B → · d s → = 0 equation is not according to the following

The number of magnetic lines leaving a surface is not equal to that of entering the surface.

The net magnetic flux enclosed by any closed surface is zero.

No isolated magnetic poles are available.

The magnetic flux is positive at some place and it is negative at some other place.

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Gauss law for magnetism states that the magnetic flux through any closed surface is equal to the magnetic charge enclosed by the surface divided by permeability.

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Important Questions on Magnetism and Matter

MEDIUM

Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

Two short bar magnets of moments

512 A m^{2}

and

1000 A m^{2}

are placed coaxially

18 cm

apart. The magnetic field is zero at a point

Q

between them. The field at

Q

, when one of the magnets is reversed pole to pole is

EASY

Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

The net magnetic flux through any closed surface is:

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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

A small bar magnet is placed with its axis at

30^{o}

with an external magnetic field of

0.06 T

experiences a torque of

0.018 Nm

. The minimum work required to rotate it from its stable to unstable equilibrium position is:

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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

The $B - H$ Curve of a ferromagnetic material is as shown in figure:

Question Image

A solenoid has a core of a material with relative permeability $400$ . The windings of the solenoid are insulated from the core and carry a current of $2 A$ . If the number of turns is $1000$ Per metre, calculate magnetic intensity $(H)$ and magnetic field $(B)$ .

HARD

Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

Which of the field pattern given below is valid for electric field as well as for magnetic field?

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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

What do you understand by Permanent magnets and electromagnet? Give uses of electromagnet.

MEDIUM

Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

Two identical bar magnets are held perpendicular to each other with a certain separation, as shown below. The area around the magnets is divided into four zones.
Question Image

Given that there is a neutral point it is located in,

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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

A hoop and a solid cylinder of same mass and radius are made of a permanent magnetic material with their respective axes. But the magnetic moment of hoop is twice of solid cylinder. They are placed in a uniform magnetic field in such a manner that their magnetic moments make a small angle with the field. If the oscillation periods of hoop and cylinder are

T_{h}

and

T_{c}

respectively, then:

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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

State Gauss’ law for magnetism. Explain its significance.

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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

Why magnetic lines of force do not intersect each other?

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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

The $B - H$ Curve of a ferromagnetic material is as shown in figure:

Question Image

$(b)$ Identify the value of retentivity and coercivity from the figure.

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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

An electron gun is placed inside a long solenoid of radius

R

on its axis. The solenoid has

n

turns/length and carries a current

I .

The electron gun shoots an electron along the radius of the solenoid with speed

v .

If the electron does not hit the surface of the solenoid, maximum possible value of

v

is (all symbols have their standard meaning):

Question Image

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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

Assertion: The magnetic field lines are continuous and form closed loops.

Reason: Magnetic monopole does not exist.

The correct option among the following is

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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

If a magnet of pole strength

m

is divided into four parts such that the length and width of each small part is half that of initial one, then the pole strength of each parts will be

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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

_____ Law of magnetism establishes that monopoles do not exist.

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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

Two short bar magnets of length

1 cm

each have magnetic moments

1 .20 A m^{2}

and

1 .00 A m^{2}

respectively. They are placed on a horizontal table parallel to each other with their

N

poles pointing towards the south. They have a common magnetic equator and are separated by a distance of

20 .0 cm

. The value of the resultant horizontal magnetic induction at the mid-point

O

of the line joining their centres is close to
( Horizontal component of earth's magnetic induction is

3 .6 \times 10^{- 5} Wb m^{- 2}

)

MEDIUM

Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

An insulating thin rod of length

l

has a linear charge density

ρ (x) = ρ_{0} \frac{x}{l}

on it. The rod is rotated about an axis passing through the origin

(x = 0)

and perpendicular to the rod. If the rod makes

n

rotations per second, then the time averaged magnetic moment of the rod is:

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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

State Gauss Law for Magnetism.

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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

\oint \vec{B} \cdot d \vec{s} = 0

equation is not according to the following

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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetism and Gauss's Law

An electron is moving along

+ x

direction with a velocity of

6 \times 10^{6} {ms}^{- 1}

. It enters a region of uniform electric field of

300 V / c m

pointing along

+ y

direction. The magnitude and direction of the magnetic field set up in this region such that the electron keeps moving along the x direction will be:

Gauss law for magnetism states that the magnetic flux through any closed surface is equal to the magnetic charge enclosed by the surface divided by permeability.

Important Questions on Magnetism and Matter

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