BlogIIT-JEEHc Verma Solutions Class 12 Chapter 12 Magnetic Field

Hc Verma Solutions Class 12 Chapter 12 Magnetic Field

A magnetic field, a vector field near a magnet, an electric current, or a changing electric field that allows magnetic forces to be observed. Magnetic fields, like those found on Earth, cause magnetic compass needles and other permanent magnets to align in the direction of the field. Electrically charged particles move in a circular or helical pattern as a result of magnetic fields. This force, which is exerted on electric currents in wires in a magnetic field, is the basis for the operation of electric motors. When a permanent magnet or a wire carrying a steady electric current in one direction is surrounded by a magnetic field, it becomes stationary and is referred to as a magnetostatic field. At any given point, its magnitude and direction remain constant. The magnetic field around an alternating current or a fluctuating direct current changes in magnitude and direction all the time. Magnetic fields can be represented by continuous lines of force or magnetic flux that emerge from north-seeking magnetic poles and enter south-seeking magnetic poles. The magnitude of the magnetic field is indicated by the density of the lines. The field lines are crowded together, or denser, at the poles of a magnet, for example, where the magnetic field is strong. As the magnetic field weakens, they fan out further away, becoming less dense. Parallel straight lines with equal spacing represent a uniform magnetic field.

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    The flux direction is the same as the north-seeking pole of a small magnet. A magnetic field is a vector field that can be observed to have magnetic forces in the vicinity of a magnet, an electric current, or a changing electric field. Moving electric charges and intrinsic magnetic moments of elementary particles associated with a fundamental quantum property known as spin generate a magnetic field. Magnetic and electric fields are inextricably linked and both components of the electromagnetic force, one of nature’s four fundamental forces.

    Solved Solutions

    Question: Can a magnetic field accelerate a charged particle? Is it possible to increase its speed?


    A magnetic field can, in fact, accelerate a charged particle. A magnetic field acts on a charged particle that is perpendicular to both the magnetic field and the velocity. If the charged particle is initially moving at a right angle to the magnetic field, the particle’s trajectory will be circular. The magnitude of the velocity remains constant in circular motion, but the direction changes continuously. As a result, the motion is accelerated while the speed remains constant.

    Question: Will a current loop in a magnetic field always have zero force?

    Solution: No, it depends on the magnetic field, specifically whether it is uniform or non-uniform, as well as the orientation of the current loop.
    If the magnetic field is parallel to the plane of the loop in a uniform magnetic field, the force on the circular loop is zero; in a non-uniform magnetic field, the force may or may not be zero.

    Question: A circular loop with an area of 1 cm2 and a current of 10 A is placed in a magnetic field of 0.1 T perpendicular to the loop’s plane. The magnetic field torque on the loop is

    (a) zero
    (b) 10−4 N m
    (c) 10−2 N m
    (d) 1 N m

    Solution: (a) zero

    A circular loop always experiences zero toques when placed in a uniform magnetic field. We all know that when a current-carrying wire is placed in an external magnetic field, it experiences a force. Forces, on the other hand, are present in pairs in the case of a circular loop, i.e. they are equal and opposite in magnitude. As a result, for every point on the loop, there is another point on the diametrically opposite edge where the force is equal to and opposite to the force acting on the first point. As a result, these two forces cancel each other out. When placed in a uniform magnetic field, the net torque on the loop is always zero.


    Determine the magnetic flux density.

    Magnetic flux density is the amount of magnetic flux in a given area measured perpendicular to the direction of the magnetic flux. It is denoted by the symbol B and is measured in Tesla units.

    Are magnetic fields present in space?

    Yes, magnetic fields exist in space. Based on studies of a large number of pulsars and the polarisation of their radio signals, the spiral arms of the Milky Way appear to have a very large-scale organised magnetic field. Magnetic fields have been discovered in interstellar dust clouds. The fields are amplified as the clouds collapse.

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