Define angle of dip, magnetic meridian, geographic meridian and angle of declination and obtain the relation, tanθ = B V B H , Where θ is angle of dip. B V and B H are vertical and horizontal components of earth's magnetic field.

(i) Angle of Declination : The vertical plane passing through the axis of a magnetic needle suspended freely through its centre of gravity and at rest under the earth’s field is called the ‘magnetic meridian’. Similarly, the vertical plane passing through the line joining the geographical north and south poles is called the geographical meridian. At any place the acute angle between the magnetic meridian and the geographical meridian is called the ‘angle of declination' α . Both magnetic meridian and declination are not defined at the magnetic poles of the earth. (ii) Angle of Dip or Magnetic Inclination : If a magnetic needle is pivoted on a horizontal axis through its centre of gravity so that it is free to rotate in a vertical plane then, in the steady state in magnetic meridian, the needle dips down with respect to the horizontal. This type of needle is called the ‘dip needle’. In the northern hemisphere, the north pole of the magnetic needle inclines downwards , whereas in the southern hemisphere the south pole of the needle inclines downwards. In this state, the angle between the axis of the needle in the magnetic meridian and the horizontal direction is called the ‘angle of dip’. The magnetic axis of the needle represents the direction of the earth’s magnetic field. Hence, the angle of dip at a place is the angle between the direction of earth*s magnetic field and the horizontal in the magnetic meridian at that place. Relation:- from the figure B H = B E c o s θ B V = B E s i n θ Where θ is angle of dip .These equation give B E = B H 2 + B V 2 and B V B H = t a n θ

A small magnetic needle of magnetic moment 4 . 8 × 10 - 2 J T - 1 is placed at 30 ° with a uniform external magnetic field B → of magnitude 3 . 0 × 10 - 2 T . What is the magnitude and direction of the torque acting on the needle?

Given, The magnetic moment of a small Magnetic needle = 4 . 8 × 10 - 2 J T - 1 A uniform external magnetic field= 3 . 0 × 10 - 2 T Angle = 30 o For magnitude and direction of torque on a needle is 𝜏 = mBsinθ = 4 .8 × 10 − 2 × 3 × 10 − 2 × 1 2 = 7 . 2 × 10 − 4 Nm Duration of torque is such that the needle lies along B → .

E M B I B E

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 9 - Magnetic Field and Earth's Magnetism>QUESTIONS>Q 1

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12th ICSE

IMPORTANT

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Define magnetic dipole moment in terms of current and area of a loop and in terms of pole strength of a magnetic dipole. Write unit of magnetic dipole and pole strength.

Important Questions on Magnetic Field and Earth's Magnetism

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12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 9 - Magnetic Field and Earth's Magnetism>QUESTIONS>Q 2

Compare current carrying loop and a bar-magnet as a magnetic dipole. Obtain an expression for magnetic field due to a magnetic dipole at equatorial line.

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IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 9 - Magnetic Field and Earth's Magnetism>QUESTIONS>Q 3

Draw a diagram of Earth's magnetic field, showing a horizontal, vertical component of Earth's magnetic field and angle of dip.

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12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 9 - Magnetic Field and Earth's Magnetism>QUESTIONS>Q 4

Name the places on earth where horizontal and vertical components are minimum and maximum.

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12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 9 - Magnetic Field and Earth's Magnetism>QUESTIONS>Q 4

Name the places on earth where angle of dip is maximum and minimum.

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12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 9 - Magnetic Field and Earth's Magnetism>QUESTIONS>Q 4

Name the places on Earth where what is reason for earth's magnetism?

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12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 9 - Magnetic Field and Earth's Magnetism>QUESTIONS>Q 5

Explain magnetic lines of force and write properties. Draw diagram.

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12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 9 - Magnetic Field and Earth's Magnetism>QUESTIONS>Q 6

Define angle of dip, magnetic meridian, geographic meridian and angle of declination and obtain the relation, $tanθ = \frac{B_{V}}{B_{H}}$ , Where $θ$ is angle of dip.

$B_{V}$ and $B_{H}$ are vertical and horizontal components of earth's magnetic field.

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12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 9 - Magnetic Field and Earth's Magnetism>QUESTIONS>Q 1

A small magnetic needle of magnetic moment