Physics M.C.Q (1 Marks)

They are ways of switching using a low current to use an electromagnet to close or open a spring steel contact.They are often used to isolate a user from a high voltage that needs to be switched, using low current, low voltage to operate the relay, rather than having a user come in direct proximity to the higher voltage that needs to be switched.When the current through the electromagnet of a relay reaches a particular value it either breaks the circuit by repllening or closes the circuit by pulling in an iron contact.

Lenz's law deals with conversion of mechanical energy into electromagnetic energy in case of electromagnetic induction. Hence Lenz's law is basically a conversion of energy from one form to another.

Permanent magnets should have high retentivity so that a strong magnetic field persists on removal of magnetic field.
Permanent magnets should have high coercivity so that external magnetic field in opposite direction cannot easily demagnetize the magnet.

Permanent magnet should have large coercivity and large retentivity. Therefore, the hysteresis cycle of the material should be tall and wide.

The permanent magnetic moment of the atoms of a material is zero. The material must be diamagnetic.

Like magnetic force repel each other whereas unlike magnetic poles attract each other.

A magnetic field is generated when electric charge carriers such as electrons move through space or within an electrical conductor. It is the space surrounding the magnet in which magnetic force acts. Its intensity is represented by magnetic lines of force.

Coercivity is the magnetic force required to demagnetise the material.

Unlike paramagnetic materials, the atomic moments in ferromagnetic materials exhibit very strong interactions. These interactions are produced by electronic exchange forces and result in a parallel or antiparallel alignment of atomic moments.
This results in permanent non-zero magnetic moment of atoms in these materials.

Lenz's Law states that the direction of an induced current is always such as to oppose the change in the circuit or the magnetic field that produces it. So according to this law, induced current flows to oppose the cause.

A moving charge and changing electric field both produces magnetic field.

A narrow hysteresis loop implies a small amount of dissipated energy. This occurs as a result of its small area and therefore more frequently repeated reversals of applied magnetising force. Soft magnetic are materials used in devices that require alternating magnetic fields have these narrow hysteresis shapes.

Ferromagnetic substance, Because they get magnetize in external magnetic field and don't lose their magnetic property.

An electric current is produced in the wire. The production of electricity from magnetism is called electromagnetic induction.

A surrounding around a magnet in which source is felt is due to magnetic property of the magnet term as magnetic field.

The statement magnetic intensity and intensity of magnetization are the same is the false one. They are not the same. When a magnet is entering a magnetic field, then the poles of the magnet experiences certain forces. Magnetic intensity refers to the measure of these forces. But, the intensity of magnetization explains the change in the magnetic moment of a magnet as a function of volume. All the other statements are valid.

Artificial magnets are man-made magnets. Magnets that are made from iron in different components shapes and sizes for different uses are called artificial magnets.

Magnetization is also termed as magnetic polarization. Magnetic polarization is basically a balance between the magnetic flux density in a space which is devoid of matter and the magnetic flux density in a space with matter, i.e. in a material.

Since the coil and the magnet are moving with same velocity, so there will be no change in magnetic flux linked with the coil due to magnet. Hence no emf is induced in the coil.

When a charge electron starts to move, electric current generates and this electric current generates magnetic field, a charge at rest also can generate electric field.

A vertical plane passing through the axis of a freely suspended or pivoted magnet is known as magnetic meridian of Earth. The vertical plane passing through the geographical North Pole and South Pole at a given place is known as the geographical meridian of that place.

Explanation:
When a ferromagnetic material goes through a Hysteresis loop, the Magnetic susceptibility may be zero, may be infinity or may be negative.

In superconductors, the resistance drops abruptly to zero when the material is cooled below its critical temperature. Thus resistivity of superconductors is zero below its critical temperature.