N.C.E.R.T. Simplified

Q. What is the magnetic effect of electric current? A.  Magnetic effect of electric current means that an electric current flowing through a conductor produces a magnetic field around it. Q. What is a magnet? A.  A magnet is an object which attracts iron, steel, nickel, and cobalt.   Q. What are the north and south poles of a magnet? A.  The end of a freely suspended (/pivoted) magnet which points towards the north direction is called the north pole of the magnet. The end of a freely pivoted magnet which points towards the south direction is called the south pole of a magnet. Q. Write a few uses of magnets. A.  i) Magnets are used in electronic goods like radios, televisions, speakers, refrigerators, audio and video cassette tapes, hard discs, computers, toys etc. ii) Magnets are also used in making electric generators and electric motors. iii) Magnets are used in the working of MRI (Magnetic Resonance  Image ) technique which is used...

Q. Define density and relative density. Give their S.I. units. A.   Density: It is the mass of substance per unit volume. S.I. unit of density is kg/m³. Relative density:  It is the ratio of the density of a substance to that of water. Q. Define thrust and pressure. Give their S.I. units. A. Thrust:  It is the force acting on an object, perpendicular to its surface. S.I. unit of thrust is N (Newton). Pressure:  It is the perpendicular force acting on a unit area. S.I. unit is Pascal (Pa) i.e. N/m². Q. Explain why a sharp knife cuts better than a blunt knife. A.  The area on which the force acts decreases if we use a sharp knife and thus the pressure and effect of force increases (P∝1/A). Hence a sharp knife cuts better than a blunt knife. Q. Explain why tanks are made to run over broad steel tracks? A. Broad steel tracks increase the area of contact between the tank and the ground. This reduces the pressure on the ground and prevents the tank ...

                                Ch.10 - Gravitation Q1.  How does the force of gravitation between 2 objects change when the distance between them is reduced to half? A1.  The masses of the 2 objects are M and m        Distance = r/2        Force = GMm/ (r/2)^2                  = GMm/ (r^2/4)                  = 4GMm/ r^2 Q2.  Gravitational force acts on all objects in proportion to their masses. Why then a heavy object does not fall faster than a light object? A2.  The acceleration on the objects does not depend on their masses. The acceleration due to gravity is same on all objects. Thus ideally, a heavy object and light object fall at the same time, but in real life situations, heavy objects fall faster due to the variation in the effect...