1.What do you mean by magnetic meridian?
Ans. When bar magnet is suspended with a string from middle, it sets itself in north & south direction. The plane passing I through axis of magnet is called magnetic meridian.
02. What do you mean by neutral point?
Ans. The point where net induction is zero is called a neutral point. The magnetic force field in which the magnetic lines of force are drawn is made up of two fields. First is horizontal component (B) of earth’s magnetic force field and the other is magnetic force field of magnet. So we say that those points where B, and magnetic force field of magnet balances each other are called neutral points.
03. According to modern theory of magnetism, what is the causes of magnetism?
Ans.-Modern theory of magnetism-The atomic model of magnet is concerned with atomic structure. In each atom there is a positively charged nucleus around which electrons revolve in different orbits. The orbital motion of electron is equivalent to an elementary current.
Due to orbital motion of electron magnetism is produced & there is magnetic moment. Besides orbital motion there is spin liked to electron; magnetic moment is also exist due to this spin. So, the net magnetic moment is resultant of the two magnetic moments.
03. What is magnetic storm?
Ans. Beside regular changes there is sometime violent & sudden change in sun’s magnetic field. It is called magnetic storm.
04. What do you mean by apparent dip angle at any place?
Ans.-Apparent dip angle: The angle between the magnetic meridian and the geographical meridian at a place is called apparent dip angle. This occurs when the dip circle does not lies on magnetic meridian.
05. Define Magnetic potential.
Ans. Magnetic potential: The amount of workdone to carry the unit north pole from infinity to any point in the magnetic field is called magnetic potential at that point. It is denoted by V. Its SI unit is volt. It is a scalar.
06. Why core of transformer is laminated?
Ans. It is done to prevent induction of eddy current and to minimize iron loss. When a metal plate is kept in a varying magnetic field, a current is always induced in the plate which is of whirling nature. There is a loss of energy due to induction of current. So, to prevent induction of eddy current iron core of transformer is laminated. [2]
07. When current flows through the coil of a transformer, then the core is heated. Why?
Ans. When current flows (A.C.) through the coil of the transformer, the core is magnetized and demagnetized alternately. The energy taken at the time of magnetization is not evolved totally at the time of demagnetization. Some energy remains in core which appears in the form of heat.
08. Sometimes it is seen that when electric bulb is suddenly switched off the bulb gets fused. Why?
Ans. When the circuit is switched off the current becomes zero from maximum, so, the rate of change in flux (rate of decreasing) becomes very high. As a result, due to self induction, e.m.f. of high value is generated. A strong instantaneous current flow along with the induced main current. As a result of heating effect, the bulb gets fused.
