Tamil Nadu HSE Second Year Physics key terms

The measure of the number of electric field lines passing through a given area; it equals the product of field strength, area, and the cosine of the angle between the field and the area normal. Unit: volt metre.

A law stating that the total electric flux through any closed surface equals the net charge enclosed divided by the permittivity of free space. It is used to find fields of symmetric charge distributions.

The ability of a conductor or capacitor to store electric charge per unit potential difference. It equals charge divided by voltage and is measured in farads.

The ratio of the permittivity of a material to the permittivity of free space; it shows how much a dielectric reduces the electric field and increases capacitance compared with vacuum.

The small average velocity with which free electrons move along a conductor in the direction opposite to an applied electric field, superimposed on their random thermal motion.

The drift velocity acquired by a charge carrier per unit applied electric field. It is measured in square metres per volt second and is higher for electrons than for holes in silicon.

A property of a material that measures how strongly it opposes the flow of electric current; it equals resistance times cross-sectional area divided by length, in ohm metre.

Two rules for analysing circuits: the junction rule says currents entering a junction equal those leaving; the loop rule says the sum of potential differences around any closed loop is zero.

A vector for a current loop or magnet giving its strength and orientation; it equals current times loop area and points along the axis according to the right-hand rule. Unit: ampere square metre.

A law stating that the line integral of the magnetic field around any closed path equals the permeability of free space times the net current enclosed by that path.

An instrument that detects small currents by the deflection of a coil suspended in a magnetic field; the deflection is proportional to current, and a radial field makes the scale linear.

The total force on a charge moving in electric and magnetic fields; the magnetic part acts perpendicular to both the velocity and the field and does no work.

The number of magnetic field lines crossing a surface; it equals field strength times area times the cosine of the angle between the field and the surface normal. Unit: weber.

A law stating that the induced emf in a circuit equals the negative rate of change of magnetic flux linked with it; more turns or faster flux change give a larger emf.

A rule stating that an induced current always flows in a direction that opposes the change in magnetic flux producing it, so that mechanical work must be done to generate electrical energy.

The property of a coil by which a changing current in it induces an emf in the same coil opposing the change; it equals flux linkage per unit current, in henry.

The total opposition offered by a circuit containing resistance, inductance and capacitance to alternating current; it is the vector sum of resistance and reactance, measured in ohm.

A device that changes an alternating voltage using two coils wound on a common iron core; the voltage ratio equals the turns ratio, and power is nearly conserved in an ideal transformer.

The complete reflection of light back into a denser medium when it strikes the boundary with a rarer medium at an angle greater than the critical angle.

The angle of incidence in the denser medium for which the refracted ray grazes the boundary between two media; beyond it total internal reflection occurs.

The modification of light intensity produced when two coherent waves superpose, giving alternate bright and dark fringes where the waves arrive in phase or out of phase.

The bending of light around the edges of an obstacle or through a narrow slit, producing a pattern of bright and dark bands due to superposition of secondary wavelets.

The emission of electrons from a metal surface when light of sufficiently high frequency falls on it; the emitted electrons are called photoelectrons and their number depends on intensity.

The minimum energy needed to remove an electron from the surface of a metal. It is characteristic of the metal and is usually expressed in electron volt.

The lowest frequency of incident light that can cause photoelectric emission from a given metal surface; below it no electrons are emitted however intense the light.

The wavelength associated with a moving particle, equal to Planck's constant divided by its momentum; it explains wave behaviour of electrons and other matter.

The time taken for half the radioactive nuclei in a sample to decay; it is constant for a given isotope and does not depend on temperature or chemical state.

The difference between the total mass of the nucleons in a nucleus taken separately and the actual mass of the nucleus; it appears as binding energy.

The energy required to separate all the nucleons of a nucleus completely; it equals the mass defect multiplied by the square of the speed of light.

The splitting of a heavy nucleus into two lighter nuclei of comparable mass, accompanied by the release of a large amount of energy and usually two or three neutrons.

A pure semiconductor with no added impurity, in which the number of free electrons equals the number of holes and conductivity is low at room temperature.

The deliberate addition of a small amount of a suitable impurity to a pure semiconductor to increase its conductivity by providing extra free electrons or holes.

The thin layer at a p-n junction where mobile charge carriers have diffused away, leaving fixed ionised atoms and creating a built-in potential barrier.

The conversion of alternating current into direct current using a diode, which allows current to pass mainly in one direction; a full-wave rectifier uses two or four diodes.

A heavily doped diode designed to operate safely in reverse breakdown, where the voltage stays nearly constant; it is used to regulate voltage in circuits.

The process of varying a property of a high-frequency carrier wave, such as its amplitude or frequency, in accordance with a low-frequency information signal so it can be transmitted.

A modulation in which the amplitude of a high-frequency carrier wave is varied in step with the audio or information signal while the frequency stays constant.

The process carried out at the receiver of extracting the original information signal from a modulated carrier wave, usually after the signal has been amplified.