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Which one of the following is a natural magnet?
(Choose from lodestone or bar magnet).

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Important Questions on Fun With Magnets

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Science>Physics>Fun With Magnets>Discovery of Magnets

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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Science>Physics>Fun With Magnets>Discovery of Magnets

Following figures show the arrangement of bar magnets in different configurations. Each magnet has magnetic dipole

\vec{m} .

Which configuration has highest net magnetic dipole moment?

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Science>Physics>Fun With Magnets>Discovery of Magnets

The magnetic dipole moment of a short magnetic dipole at a distant point along the equator of magnet has a magnitude of

X

in SI units. If the distance between point and the magnet is halved then the magnitude of dipole moment will be

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Science>Physics>Fun With Magnets>Discovery of Magnets

A thin rod of length

L

is magnetized and has magnetic moment

M

. The rod is then bent in a semicircular arc. The magnetic moment in the new shape is

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Science>Physics>Fun With Magnets>Discovery of Magnets

The magnetic flux near the axis and inside the air-core solenoid of length

60 cm

carrying current

I

1.57 \times 10^{6} Wb .

Its magnetic moment will be (cross-sectional area of a solenoid is very small as compared to its length,

μ_{0} = 4 π \times 10^{- 7}

SI units)

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Science>Physics>Fun With Magnets>Discovery of Magnets

A wire of length

L

metre carrying a current of

I

ampere is bent in the form of a circle. Its magnetic moment is,

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Science>Physics>Fun With Magnets>Discovery of Magnets

Torque acting on a rectangular coil carrying current

i

situated parallel to magnetic field of induction

B

, having the number of turns

n

and area

A

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Science>Physics>Fun With Magnets>Discovery of Magnets

A bar magnet of length

14 cm

is placed in the magnetic meridian with its north pole pointing towards the geographic north pole. A neutral point is obtained at a distance of

18 cm

from the center of the magnet. If

B_{H} = 0.4 G

, the magnetic moment of the magnet is

(1 G = 10^{- 4} T)

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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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Science>Physics>Fun With Magnets>Discovery of Magnets

A circular coil having

N

turns and radius

r

carries a current

I .

It is held in the

X Z

plane in a magnetic field

B \hat{i}

. The torque on the coil due to the magnetic field is:

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Science>Physics>Fun With Magnets>Discovery of Magnets

In a permanent magnet at room temperature

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Science>Physics>Fun With Magnets>Discovery of Magnets

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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Science>Physics>Fun With Magnets>Discovery of Magnets

The ratio of the magnetic field at the centre of a current-carrying circular coil to magnetic moment is $x$ . If the current and the radius both are doubled. The new ratio will become

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Science>Physics>Fun With Magnets>Discovery of Magnets

An iron rod of volume

10^{- 3} m^{3}

and relative permeability

1000

is placed as core in a solenoid with

10 turns {cm}^{- 1}

. If a current of

0.5 A

is passed through the solenoid, then the magnetic moment of the rod will be :

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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

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Science>Physics>Fun With Magnets>Discovery of Magnets

A long magnetic needle of length

2 l

magnetic moment

M

and pole strength

m

is broken into two pieces at the middle. The magnetic moment and pole strength of each piece will be

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Science>Physics>Fun With Magnets>Discovery of Magnets

A large magnet is broken into two pieces so that their lengths are in the ratio

1 : 2

. The ratio of their magnetic moments is

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Science>Physics>Fun With Magnets>Discovery of Magnets

A square loop is carrying a steady current

I

and the magnitude of its magnetic dipole moment is

m

. If this square loop is changed to a circular loop and it carries the same current, the magnitude of the magnetic dipole moment of circular loop will be:

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Science>Physics>Fun With Magnets>Discovery of Magnets

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}

)

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Science>Physics>Fun With Magnets>Discovery of Magnets

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:

Which one of the following is a natural magnet? (Choose from lodestone or bar magnet).

Important Questions on Fun With Magnets

Learn and Prepare for any exam you want !

Which one of the following is a natural magnet?
(Choose from lodestone or bar magnet).