Magnetism And Matter

Question

A closely wound solenoid of 2000 turns and area of cross-section 1.6 x 10^–4 m², carrying a current of 4.0 A, is suspended through its centre allowing it to turn in a horizontal plane.
(a) What is the magnetic moment associated with the solenoid?
(b) What is the force and torque on the solenoid if a uniform horizontal magnetic field of 7.5 x 10^–2 T is set up at an angle of 30° with the axis of the solenoid?

Solution

(a) Given,
Number of turns of coil, N = 2000
Area of cross-section of solenoid, A= 1.6 x 10^–4 m²Current passing through the coil, I = 4 A

Magnetic moment , M = NIA

= 2000 \times 4 \times 1.6 \times 10^{- 4} = 1.28 {Am}^{2}

The direction of

\vec{M}

is along the axis of the solenoid in the direction related to the sense of current via the right handed screw rule.

(b) Uniform magnetic field applies, B = 7.5 x 10^–2 T
Angle between the axis of the solenoid and magnetic field,

θ

= 30°
Since the magnetic field is uniform on the solenoid, force acting on the solenoid is 0.

Torque is given by,

τ = MB \sin θ = 1.28 \times 7.5 \times 10^{- 2} \sin 30 ° = 1.28 \times 7.5 \times 10^{- 2} \times \frac{1}{2} J = 0.048 J .

The direction of the torque is such that the solenoid tends to align the axis of the solenoid (magnetic moment vector) along the direction of magnetic field

\vec{B}

Some More Questions From Magnetism and Matter Chapter

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The earth's magnetic field varies from point to point in space. Does it also change with time? If so, on what time scale does it change appreciably?

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The earth's core is known to contain iron. Yet geologists do not regard this as a source of the earth's magnetism. Why?

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The charged currents in the outer conducting regions of the earth's core are thought to be responsible for earth's magnetism. What might be the ‘battery’ (i.e., the source of energy) to sustain these currents?

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Magnetism And Matter

Some More Questions From Magnetism and Matter Chapter

Answer the following question regarding earth:
A vector needs three quantities for its specification. Name the three independent quantities conventionally used to specify the earth's magnetic field.

Answer the following question regarding earth:
The angle of dip at a location in southern India is about 18°. Would you expect a greater or smaller dip angle in Britain?

Answer the following question regarding earth:
If you made a map of magnetic field lines at Melbourne in Australia, would the lines seem to go into the ground or come out of the ground?

Answer the following question regarding earth:
In which direction would a compass free to move in the vertical plane point to, if located right on the geomagnetic north or south pole?

Answer the following question regarding earth:
Geologists claim that besides the main magnetic N-S poles, there are several local poles on the earth's surface oriented in different directions. How is such a thing possible at all?

Answer the following question:
The earth's magnetic field varies from point to point in space. Does it also change with time? If so, on what time scale does it change appreciably?

Answer the following question:
The earth's core is known to contain iron. Yet geologists do not regard this as a source of the earth's magnetism. Why?

Answer the following question:
The charged currents in the outer conducting regions of the earth's core are thought to be responsible for earth's magnetism. What might be the ‘battery’ (i.e., the source of energy) to sustain these currents?

Answer the following question:
The earth may have even reversed the direction of its field several times during its history of 4 to 5 billion years. How can geologists know about the earth's field in such distant past?

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For Daily Free Study Material Join wiredfaculty

Magnetism And Matter

Some More Questions From Magnetism and Matter Chapter

Answer the following question regarding earth:A vector needs three quantities for its specification. Name the three independent quantities conventionally used to specify the earth's magnetic field.

Answer the following question regarding earth:The angle of dip at a location in southern India is about 18°. Would you expect a greater or smaller dip angle in Britain?

Answer the following question regarding earth: If you made a map of magnetic field lines at Melbourne in Australia, would the lines seem to go into the ground or come out of the ground?

Answer the following question regarding earth:In which direction would a compass free to move in the vertical plane point to, if located right on the geomagnetic north or south pole?

Answer the following question regarding earth:Geologists claim that besides the main magnetic N-S poles, there are several local poles on the earth's surface oriented in different directions. How is such a thing possible at all?

Answer the following question:The earth's magnetic field varies from point to point in space. Does it also change with time? If so, on what time scale does it change appreciably?

Answer the following question:The earth's core is known to contain iron. Yet geologists do not regard this as a source of the earth's magnetism. Why?

Answer the following question:The charged currents in the outer conducting regions of the earth's core are thought to be responsible for earth's magnetism. What might be the ‘battery’ (i.e., the source of energy) to sustain these currents?

Answer the following question:The earth may have even reversed the direction of its field several times during its history of 4 to 5 billion years. How can geologists know about the earth's field in such distant past?

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

Answer the following question regarding earth:
A vector needs three quantities for its specification. Name the three independent quantities conventionally used to specify the earth's magnetic field.

Answer the following question regarding earth:
The angle of dip at a location in southern India is about 18°. Would you expect a greater or smaller dip angle in Britain?

Answer the following question regarding earth:
If you made a map of magnetic field lines at Melbourne in Australia, would the lines seem to go into the ground or come out of the ground?

Answer the following question regarding earth:
In which direction would a compass free to move in the vertical plane point to, if located right on the geomagnetic north or south pole?

Answer the following question regarding earth:
Geologists claim that besides the main magnetic N-S poles, there are several local poles on the earth's surface oriented in different directions. How is such a thing possible at all?

Answer the following question:
The earth's magnetic field varies from point to point in space. Does it also change with time? If so, on what time scale does it change appreciably?

Answer the following question:
The earth's core is known to contain iron. Yet geologists do not regard this as a source of the earth's magnetism. Why?

Answer the following question:
The charged currents in the outer conducting regions of the earth's core are thought to be responsible for earth's magnetism. What might be the ‘battery’ (i.e., the source of energy) to sustain these currents?

Answer the following question:
The earth may have even reversed the direction of its field several times during its history of 4 to 5 billion years. How can geologists know about the earth's field in such distant past?