Advertisements
Advertisements
प्रश्न
A very long bar magnet is placed with its north pole coinciding with the centre of a circular loop carrying as electric current i. The magnetic field due to the magnet at a point on the periphery of the wire is B. The radius of the loop is a. The force on the wire is
विकल्प
very nearly 2πaiB perpendicular to the plane of the wire
2πaiB in the plane of the wire
πaiB along the magnet
zero
उत्तर
very nearly `2pi aiB` perpendicular to the plane of the wire
In this case, the north pole of the magnet is coinciding with the centre of the circular loop carrying electric current i. So, the magnetic field lines almost lie on the plane of the ring and the force due to the field lines is perpendicular to the field lines and to the plane of the circular ring.
Let idl be the current element, B be the magnetic field and dF be the force on the current element idl.
Now
`dF = B i dl ⇒ F = ∫_0^(2pia) B i dl`
⇒ `F = 2pi a iB`
Thus, the force acting on the wire is `2pi a iB` and it is perpendicular to the plane of the wire.
APPEARS IN
संबंधित प्रश्न
What are permanent magnets? Give one example ?
Why should the material used for making permanent magnets have high coercivity?
Magnetic meridian is
Which of the following four graphs may best represent the current-deflection relation in a tangent galvanometer?
Consider the situation of the previous problem. The directions of the magnetic field due to the dipole are opposite at
(a) P1 and P2
(b) Q1 and Q2
(c) P1 and Q1
(d) P2 and Q2
The desirable properties for making permanent magnets are _________________ .
The coercive force for a certain permanent magnet is 4.0 × 104 A m−1. This magnet is placed inside a long solenoid of 40 turns/cm and a current is passed in the solenoid to demagnetise it completely. Find the current.
The magnetic field due to the earth has a horizontal component of 26 μT at a place where the dip is 60°. Find the vertical component and the magnitude of the field.
A short magnet produces a deflection of 37° in a deflection magnetometer in Tan-A position when placed at a separation of 10 cm from the needle. Find the ratio of the magnetic moment of the magnet to the earth's horizontal magnetic field.
The magnetometer of the previous problem is used with the same magnet in Tan-B position. Where should the magnet be placed to produce a 37° deflection of the needle?
A short magnet makes 40 oscillations per minute when used in an oscillation magnetometer at a place where the earth's horizontal magnetic field is 25 μT. Another short magnet of magnetic moment 1.6 A m2 is placed 20 cm east of the oscillating magnet. Find the new frequency of oscillation if the magnet has its north pole (a) towards north and (b) towards south.
Answer in brief.
Explain one application of electromagnet.
A wire of length 2 m carrier of lamp is bend to form a circle. The magnetic moment of a coil is :-
A steel wire of length 1 has a magnetic moment m it is then bent into a semicircular arc. The new magnetic moment is
Which magnetic properties are desirable for making a permanent magnet?
