Part I Physics

The photoelectric effect The photoelectric effect is the emission, or ejection, of electrons from the surface of, generally, a metal in response to incident light.A material that can exhibit The photoelectric effect is said to be photoemissive, and the ejected electrons are called photoelectrons. The process was discovered by Heinrich Hertz in 1887. Attempts to explain the effect by classical electromagnetic failed. In 1905,Albert Einstein presented an explanation based on the quantum concept of Max Planck. Einstein described the photoelectric effect using a formula that relates the maximum kinetic energy (Kmax) of the photoelectrons to the frequency of the absorbed ... Read more

Solar Energy : Source, Solar heating devices, solar cooker solar cell   Sunlight is Earth’s most abundant energy source and is delivered free of charge. Indeed, the energy from sunlight reaching the land surface of the earth  is thousands of times greater than the world’s current total annual consumption of energy. Yet harnessing sunlight’s energy content directly—rather than indirectly in fossil fuels, wind, or hydroelectric power—makes only a small contribution to humanity’s energy supply. Active solar techniques include the use of photovoltaic systems, concentrated solar power and solar water heating to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light-dispersing properties, ... Read more

Electric current Ohm’s law and Resistance   Electrical current is the flow of charged particles. The flow of charges will be constant in current electricity. Electric current flows from higher electric potential to lower electric potential. For the current to flow, it requires a circuit which is closed loop of a conducting material. The circuit consists of wires which are connected end to end and the electrons flow in same direction. A circuit has conductors (wire), switch, load and a power source. The circuit starts and stops at the same point. Usually copper wires are used as conductors without insulation. ... Read more

precautions observed in electric experiments and Chemical effects of electric current When it comes to working with electrical equipment, putting safety precautions in place for any electrical project is always a top priority. From basic knowledge and equipment safety to personal precautions and equipment performance, knowing what to do to help prevent injuries and ensure safety can be a lifesaver. Avoid Water  A critical precaution when working with electrical equipment is staying out of water. If you’re working in an area where there is a good chance you’ll be around it, wear rubber boots at all times, but avoid standing ... Read more

Thermal effect of current it’s use, calculation of power and electrical energy Spent When an electric current flows through a conductor, electrical energy is expended n over coming the frictional resistance between eh electrons and the molecules of the wire. If potential difference of V volts is applied across a conductor and current of I amperes flows through it for time of t seconds, then energy expended will be equal to VIt watt-secs or joules. If R is the resistance of the conductor through which a current of I amperes flows and V is the potential difference applied across its ... Read more

Electricity and its effects -electric intensity, potential, potential difference Electricity is the physical flow of electrons, referred to as an electrical current. Electricity is an energy carrier that efficiently delivers the energy found in primary sources to end users, who in turn convert it into energy services. Electricity can be created in three ways: The most common is through electro-magnetic conversion, where electricity is generated by moving an electric conductor, such as a wire, inside a magnetic field. The most practical example of this method is a generator connected to a turbine. The turbine provides the motion required to move ... Read more

Electric discharge in gases Electrical discharge through gases is studied by using a specially designed glass tube commonly called as a discharge tube. It consists of a cylindrical glass tube having a side tube, and two metallic electrodes one at each end. These electrodes can be connected to the respective terminals of a high tension power supply. Air from inside the tube can be pumped out by connecting the side tube to a vacuum pump, and a desired pressure can be maintained inside the tube. It was found that gases could not conduct electricity even when an electrical potential of ... Read more

Ray optics Nature of light Light is a transverse, electromagnetic wave that can be seen by humans. The wave nature of light was first illustrated through experiments on diffraction and interference. Like all electromagnetic waves, light can travel through a vacuum. The transverse nature of light can be demonstrated through polarization. Light is produced by one of two methods: Incandescence is the emission of light from “hot” matter (T ≳ 800 K). Luminescence is the emission of light when excited electrons fall to lower energy levels (in matter that may or may not be “hot”). Reflection of light Reflection of ... Read more

Relation between focal length and redius of curvature The focal length (f) of a lens is the distance between the center of the lens and the point at which the reflected light, of a beam of light travelling parallel to the center line, meets the center line (principal axis). The radius of curvature (r) is the radius of the lens that forms a complete sphere. Determination of focal length of concave miror by single pin method Determine the approximate focal length of the given concave mirror by obtaining on the wall the image of a distant tree. Mount the given ... Read more