Conductors, insulators and semi-conductors i) An insulatoris a material or object which resists flow of heat (thermal insulator) or electrical charges (electrical insulators). Examples are paraffin, wood, rubber, plastics etc. ii) Conductorsare materials that contain free electrons which carry an electrical charge from one point to another. Examples are metals and non-metals like carbon, graphite …
Introduction Radioactivity was discovered by Henri Becquerel in 1869. In 1898, Marie and Pierre Curie succeeded in chemically isolating two radioactive elements, Polonium (z=84) and Radium (z= 88). Radioactivity or radioactive decay is the spontaneous disintegration of unstable nuclides to form stable ones with the emission of radiation. Unstable nuclides continue to disintegrate until a …
Photoelectric effect was discovered by Heinrich Hertz in 1887. Photoelectric effect is a phenomenon in which electrons are emitted from the surface of a substance when certain electromagnetic radiation falls on it. Metal surfaces require ultra-violet radiation while caesium oxide needs a visible light i.e. optical spectrum (sunlight). Work function A minimum amount of …
Electromagnetism is the effect resulting from the interaction between an electric current and a magnetic field. This effect brings about induced electromagnetic force (e.m.f) and the resulting current is called induced current. Experiments on electromagnetic induction When the wire is moved up the galvanometer deflects in one direction then the opposite direction when moved …
What is Electromagnetic?. Electromagnetic spectrum is a continuum of all electromagnetic waves arranged according to frequency and wavelength. It includes visible light, ultra-violet rays, microwaves, X-rays, radio waves and gamma rays. Electromagnetic waves are produced when electrically charged particles oscillate or change energy in some way. The waves travel perpendicularly to both electric and magnetic …
Introduction Circular motion is the motion of bodies travelling in circular paths. Uniform circular motion occurs when the speed of a body moving in a circular path is constant. This can be defined as motion of an object at a constant speed along a curved path of constant radius. When acceleration (variation of velocities) …
Any object in a liquid whether floating or submerged experiences an upward force from the liquid; the force is known as upthrust force. Upthrust force is also known as buoyant force and is denoted by letter ‘u’. Archimedes’ principle Floating and Sinking Archimedes, a Greek scientist carried out first experiments to measure upthrust on …
Pressure law This law states that “the pressure of a fixed mass of a gas is directly proportional to the absolute temperature if the volume is kept constant”. The comparison between Kelvin scale and degrees Celsius is given by; θ0 = (273 + θ) K, and T (K) = (T – 273) 0C. Examples A …
What is heat?. Heat is a form of energy that flows from one body to another due to temperature differences between them. Heat capacity Heat capacity is defined as the quantity of heat required to raise the temperature of a given mass of a substance by one degree Celsius or one Kelvin. It is denoted …
When current flows, electrical energy is transformed into other forms of energy i.e. light, mechanical and chemical changes. Factors affecting electrical heating Energy dissipated by current or work done as current flows depends on, a) Current b) Resistance c) Time This formula summarizes these factors as, E = I2 R t, E = I V …