If the junctions of a thermocouple are kept at constant temperature and a current is passed through the wires of the thermocouple, it has been found that one of the junction is heated and the other junction is cooled. That is heat is produced at one junction (junction which is heated) and absorbed at the … Read more
A voltaic cell is an electrochemical cell used to produce electrical energy with the help of a chemical reaction. It is the primary cell which was designated by Alessandro Volta in 1800. Construction A simple construction of a voltaic cell is shown in figure below. It consists of a copper plate and a zinc plate immersed in a … Read more
Lenz’s Law Lenz’s law is named after the physicist Emil Lenz who formulated it in 1834. It is a qualitative law that specifies the direction of induced current, but states nothing about its magnitude. Analogous to Newton’s third law in classical mechanics. It gives the direction and sign of induced emf or current. It states … Read more
All spontaneous processes tend to achieve a state of minimum energy and maximum entropy. For a system, generally it is not possible to achieve both, the minimum energy and maximum entropy simultaneously. There are cases where either of the two factors is favourable. For example, many endothermic reactions are spontaneous because the favourable entropy factor … Read more
This law is also called the law of conservation of energy. It can be stated in many ways but the following form is found to be quite useful. It states that “energy can neither be created nor destroyed. However, it can be transformed from one form into another”. This means that if certain amount of … Read more
Far and near points The eye consists of a lens L and retina R where retina is light sensitive screen. Light from the objects enters the eye through the cornea. In order to be clearly seen, the image formed by the eye-lens must appear on the retina. The ciliary muscles can change the diameter of … Read more
The energy possessed by a body because of its motion and position or state is called mechanical energy. For example: a moving car possesses energy; a stone lying at height from the ground possesses energy; a compressed or stretched spring possesses energy and so on. The mechanical energy is of two types. They are A) … Read more
The photoelectric effect showed that light consists of streams of particles called photons. This leads to the conclusion that like matter, light radiation can sometimes behave as particles. The phenomenon of interference, diffraction and polarization of the light indicate that light is wave. Light therefore, exhibits dual nature. It behaves like particle as well as … Read more
The orbital velocity of a satellite is the velocity required to be given to the satellite in order to put it in an orbit around the earth. Once the satellite is put in an orbit with required velocity, the satellite keeps on revolving around the earth. For the continuous revolution of the satellite around the … Read more
The force that acts at right angles to an imaginary line of unit length at the surface of liquid at rest is called surface tension. Simply, it can be defined as the force which is responsible for the tension at the surface of the liquid. It is one of the important properties exhibited by liquids … Read more