Tag: properties of a magnetic field

Questions Related to properties of a magnetic field

A permanent magnet in the shape of a thin cylinder of length $10$cm has magnetisation $(M) = 10^6 A m^{-1}$. It's magnetization current $I _M$ will be then

physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

  1. $10^5$A

  2. $10^6$A

  3. $10^7$A

  4. $10^8$A

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Correct Option: A
Explanation:

Given,

$M=10^6 A/m$
$l=10cm=0.1m$
Magnetization, $M=\dfrac{I _M}{l}$ 
$I _M=Ml=10^6\times 0.1$
$I _M=10^5A$
The correct option is A.

The magnetic south pole of the earth is situated near the 

physics properties of a magnetic field earth - a gigantic magnet magnetic field of earth introduction to magnetic field and magnetic flux

  1. geographic south pole

  2. geographic north pole

  3. geographic east

  4. geographic west

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Correct Option: B
Explanation:

'Magnetic North' is a LOCATION, so-named to distinguish it from True North -it has NOTHING to do with its magnetic POLARITY. The magnetic polarity at this location is south -which is why it attracts the north-seeking pole of a compass needle or magnet.

State whether true or false:

Magnetic south pole of the Earth lies close to geographic south pole of the Earth.

physics properties of a magnetic field earth - a gigantic magnet magnetic field of earth introduction to magnetic field and magnetic flux

  1. True

  2. False

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Correct Option: B
Explanation:

Magnetic south pole of the Earth lies close to geographic north pole of the Earth.

The shape of the earth's magnetic field resembles that of an imaginary

physics properties of a magnetic field earth - a gigantic magnet magnetic field of earth introduction to magnetic field and magnetic flux

  1. current-carrying circular loop

  2. solenoid

  3. U-shaped magnet

  4. bar magnet

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Correct Option: D
Explanation:

Answer is D.

A freely suspended magnet always points in the North-South direction even in the absence of any other magnet. This suggests that the Earth itself behaves as a magnet which causes a freely suspended magnet (or magnetic needle) to point always in a particular direction: North and South. The shape of the Earth's magnetic field resembles that of a bar magnet of length one-fifth of the Earth's diameter buried at its center.
The South Pole of the Earth's magnet is in the geographical North because it attracts the North Pole of the suspended magnet and vice versa. Thus, there is a magnetic S-pole near the geographical North, and a magnetic N-pole near the geographical South. The positions of the Earth's magnetic poles are not well defined on the globe; they are spread over an area. The axis of Earth's magnet and the geographical axis do no coincide. The axis of the Earth's magnetic field is inclined at an angle of about 15 degrees with the geographical axis. Due to this a freely suspended magnet makes an angle of about 15 degrees with the geographical axis and points only approximately in the North-South directions at a place.

The angle of declination at a place is the angle

physics properties of a magnetic field earth - a gigantic magnet magnetic field of earth introduction to magnetic field and magnetic flux

  1. Between the vertical plane and the geographical meridian

  2. Between the vertical plane and the magnetic meridian

  3. Between the geographical meridian and magnetic meridian

  4. Between the geographical meridian and horizontal plane

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Correct Option: C
Explanation:

A freely suspended magnet always points in the North-South direction even in the absence of any other magnet. This suggests that the Earth itself behaves as a magnet which causes a freely suspended magnet (or magnetic needle) to point always in a particular direction: North and South.

The vertical plane passing through the axis of a freely suspended magnet is called magnetic meridian. The direction of Earth's magnetic field lies in the magnetic meridian and may not be horizontal. The vertical plane passing through the true geographical North and South (or geographical axis of Earth) is called geographical meridian. The angle between the magnetic meridian and the geographic meridian at a place is called declination at that place.

It is a common notion that the earth's magnetism is due to the

physics properties of a magnetic field earth - a gigantic magnet magnetic field of earth introduction to magnetic field and magnetic flux

  1. presence of a huge permanent magnet in the interior of the earth

  2. presence of electric currents circulating in the interior of the earth

  3. influence of the sun's magnetic field

  4. influence of a nuclear explosion

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Correct Option: B
Explanation:

In the Earth, the liquid metal that makes up the outer core passes through a magnetic field which causes an electric current to flow within the liquid metal. The electric current, in turn, creates its own  magnetic field—one that is stronger than the field that created it in the first place.

Even though earth is a giant magnet, all the iron does not stick to it at north and south pole because

physics properties of a magnetic field earth - a gigantic magnet magnetic field of earth introduction to magnetic field and magnetic flux

  1. Iron is embedded in between rocks

  2. Very less iron is present near the magnetic poles of earth

  3. Force of earth's magnetism is weak

  4. Much iron is scattered away from the poles

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Correct Option: C
Explanation:
The Earth has a magnetic field which is produced deep in the interior by electrical currents in the molten part of the core.At the surface of the Earth and beyond the magnetic field is weak.It is just strong enough to rotate a small magnet, called a compass needle, balanced with little friction on a pointed support.
The Earth itself is not a magnet.The magnetic field produced in the core is much more complex in form that what would be expected for a simple magnet such as a bar magnet.The illustration of the Earth as if there is a bar magnet inside are misleading.

AN iron rod burried inside earth along direction becomes a magnet

physics properties of a magnetic field earth - a gigantic magnet magnetic field of earth introduction to magnetic field and magnetic flux

  1. N-S

  2. S-N

  3. Both

  4. None

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Correct Option: A
Explanation:

An iron rod buried inside earth along N-S direction becomes a weak magnet. It is only possible when the earth itself behaves like a magnet.

The bulging of earth at the equator and flattening at the poles is due to 

physics properties of a magnetic field earth - a gigantic magnet magnetic field of earth introduction to magnetic field and magnetic flux

  1. Centripetal force

  2. Centrifugal force

  3. Gravitational force

  4. Electrostatic force

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Correct Option: B
Explanation:

The bulging of equator and flattening at poles is due to rotation of earth. The rotation of earth creates a centrifugal force which is pseudo effect counter balancing the inward acting centripetal force. This pseudo effect pushes the earth outward, bugling from earth, and flattening at poles. 

Hence correct answer is option B.

Define angle of declination at a place :

physics properties of a magnetic field earth - a gigantic magnet magnetic field of earth introduction to magnetic field and magnetic flux

  1. angle between the vertical plane and the geographical meridian

  2. angle between the vertical plane and the magnetic meridian

  3. angle between the geographical meridian and the magnetic meridian

  4. angle between the geographical meridian and horizontal plane

Show answer
Correct Option: C
Explanation:

The magnetic meridian is an equivalent imaginary line connecting the magnetic south and north poles and can be taken as the magnetic force lines along the surface of the earth. Therefore a compass needle will be parallel to the magnetic meridian.

The angle between the magnetic and the true meridian is the angle of declination, which is relevant for navigating with a compass.