notes of class 7 physics

The third mode of energy transfer between an object and its environment is via electromagnetic waves (visible light is a kind of electromagnetic wave). Energy transferred in this way is often called thermal radiation, to distinguish it from electromagnetic signals (as in, say, television broadcast)..

Kinetic Energy and Temperature - Let us consider one-gram molecule (mole) of the gas. Let M and V be its mass and volume respectively. The pressure exerted by the gas is given by: But PV = RT where T is the absolute temperature of the gas and R is the molar gas constant. R is the gas constant for 1..

The Life of a Star - The life cycle of a star begins with the accretion of hydrogen and helium gas at -173 o C into smaller dense clouds, which contract under their own gravity. This dense cloud of gas contracting under its own gravity is called a Protostar . A cloud of gas from which a star is bor..

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For an infinitely long conductor, ..

The equation implies that since are always perpendicular, the magnetic force does no work. [This means the force cannot change the speed of the particle]. In such a case the kinetic energy remains constant. The work-energy theorem implies that work is said to be done by a force if it brings abou..

1. During constructive interference R m a x = A + B as cos f = + 1 During destructive inference cos f = -1 R m i n = A - B special case If A =B (i.e., if the two waves have same amplitude) then This indicates a good contrast between the bright and dark bands, which is required ..

1) When x = 0, P lies at the centre of the coil. So, 2) When x >> a Where pm = N I A is called the magnetic dipole moment of the current loop. Therefore, a current loop can be regarded as a magnetic dipole which produces its magnetic field. S.I unit of magnetic dipole mom..

There is a potential difference between the sphere and the metal holding the charge inside so that the alter has a positive potential relative to the sphere. (b) When the metal touches the sphere, the induced negative charge and the metal holding the charge inside, both are at the same potentia..