DEFINITION AND CONCEPT Electromagnetic waves are produced by electromagnetic vibrations. Electromagnetic waves have electrical origin and the ability to travel in vacuum. So, electromagnetic waves are regarded as a combination of traveling electric and magnetic forces which vary in value and are directed at right angles to each other and to the direction of travel. […]
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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
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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
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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
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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)
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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
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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
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Electric fields An electric field is the space around a charged body where another charged body would be acted on by a force. These fields are represented by lines of force. This line of force also called an electric flux line points in the direction of the force. Electric field patterns Just like in
Electric potential difference and electric current Electric current: Electric potential difference (p. d) is defined as the work done per unit charge in moving charge from one point to another. It is measured in volts. Electric current is the rate of flow of charge. P. d is measured using a voltmeter while current is measured
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Newton’s first law (law of inertia) This law states that “A body continues in its state of rest or uniform motion unless an unbalanced force acts on it”. The mass of a body is a measure of its inertia. Inertia is the property that keeps an object in its state of motion and resists any
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Introduction Refraction is the change of direction of light rays as they pass at an angle from one medium to another of different optical densities. Exp. To investigate the path of light through rectangular glass block. Apparatus: – soft-board, white sheet of paper, drawing pins (optical), rectangular glass block. Procedure Fix the white plain paper on
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Fluid in physics refers to liquids and gases. To study fluid flow we have to make the following assumptions: We consider fluids to be incompressible We assume that they have little or no internal friction or viscosity. Streamline and turbulent flow. The path followed by a small element of a moving fluid is called
Introduction: Oersted’s discovery. Hans Christian Oersted discovered the magnetic effect of a current in 1819. The direction of the field is dependent on the direction of the current. This discovery brought about the development of electric bells, electric motors, telephone receivers and radios. Determining the direction of the lines of force. The direction of
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Measuring length using vernier callipers. Vernier callipers is used when higher accuracy in measurement is required and this cannot be done using a metre rule. Vernier callipers has two scales; main scale and vernier scale. Outside jaws are used to measure both lengths and external diameters, inside jaws for measuring internal diameters while the tail
Work done per unit charge is called electrical potential. Current is the flow of charge. For current to be continuous, potential difference between the two points must be sustained. Sources of continuous currents. In this process work is continuously done in moving electrons against a repulsive force. A device in which the potential difference is
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Some substances get charged when rubbed against other substances i.e. nylon, plastic, paper etc. the charge acquired stays within the body i.e. it does not move and therefore known as electrostatic charge or static electricity. The law of charges – types of charges There are two types of charges i.e. negative and positive charges. The