Advertisements
Advertisements
प्रश्न
A compass needle free to turn in a horizontal plane is placed at the centre of circular coil of 30 turns and radius 12 cm. The coil is in a vertical plane making an angle of 45° with the magnetic meridian. When the current in the coil is 0.35 A, the needle points west to east.
(a) Determine the horizontal component of the earth’s magnetic field at the location.
(b) The current in the coil is reversed, and the coil is rotated about its vertical axis by an angle of 90° in the anticlockwise sense looking from above. Predict the direction of the needle. Take the magnetic declination at the places to be zero.
Advertisements
उत्तर
Number of turns in the circular coil, N = 30
Radius of the circular coil, r = 12 cm = 0.12 m
Current in the coil, I = 0.35 A
Angle of dip, δ = 45°
(a) The magnetic field due to current I, at a distance r, is given as:
B = `(μ_0 2π"NI")/(4π"r")`
Where,
μ0 = Permeability of free space = 4π × 10−7 T mA−1
∴ B = `(4π xx 10^-7 xx 2π xx 30 xx 0.35)/(4π xx 0.12)`
= 5.49 × 10−5 T
The compass needle points from West to East. Hence, the horizontal component of the earth’s magnetic field is given as:
BH = B sin δ
= 5.49 × 10−5 sin 45°
= 3.88 × 10−5 T
= 0.388 G
(b) When the current in the coil is reversed and the coil is rotated about its vertical axis by an angle of 90 º, the needle will reverse its original direction. In this case, the needle will point from East to West.
संबंधित प्रश्न
Name three elements of the earth's magnetic field which help in defining earth's magnetic field completely.
The horizontal component of the earth’s magnetic field at a place is B and angle of dip is 60°. What is the value of vertical component of earth’s magnetic field at equator?
A conducting rod held horizontally along East- West direction is dropped from rest from a certain height near the Earth’s surface. Why should there be an induced emf across the end of the rod? Draw a plot showing the instantaneous variation of emf as a function of time from the instant it begins to fall.
Where on the surface of Earth is the angle of dip zero?
Can the earth's magnetic field be vertical at a place? What will happen to a freely suspended magnet at such a place? What is the value of dip here?
Can the dip at a place be (a) zero (b) 90°?
A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It ______.
State Tangent Law in magnetism.
Choose the correct option.
The horizontal and vertical component of magnetic field of Earth are same at someplace on the surface of Earth. The magnetic dip angle at this place will be
Choose the correct option.
A place where the vertical components of Earth's magnetic field is zero has the angle of dip equal to
Answer the following question regarding earth’s magnetism:
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’s magnetism:
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?
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?
A short bar magnet placed in a horizontal plane has its axis aligned along the magnetic north-south direction. Null points are found on the axis of the magnet at 14 cm from the centre of the magnet. The earth’s magnetic field at the place is 0.36 G and the angle of dip is zero. What is the total magnetic field on the normal bisector of the magnet at the same distance as the null point (i.e., 14 cm) from the centre of the magnet? (At null points, field due to a magnet is equal and opposite to the horizontal component of earth’s magnetic field.)
Which of the following independent quantities is not used to specify the earth’s magnetic field?
The vertical component of earth’s magnetic field at a place is √3 times the horizontal component the value of angle of dip at this place is ______.
At a given place on earth’s surface the horizontal component of earth’s magnetic field is 2 × 103-5 T and resultant magnetic field is 4 × 103-5 T. The angle of dip at this place is ______.
