FSc ICS Notes Physics XII Short Questions & Definitions Chapter 13 Current Electricity

FSc ICS Notes Physics XII Short Questions & Definitions Chapter 13 Current Electricity 2nd Year Physics Notes Online Taleem Ilmi Hub

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Electricity: The nature and effects of moving or stationary electric charges.

Electric current: The rate of flow or charge past a given point in an electric circuit.

Static electricity (or Electrostatics): Electricity at rest; electric charges located on insulators.

Current electricity (or Electrodynamics): The study of the relationship between mechanical forces and magnetic and electric forces.

Shaft: Anything shaped like an arrow, as the stalk of a plant or broken handle of a cricket bat.

Carbon arc: Current flowing between two carbon electrodes,

Brush: Part of electric generator or motor which serves to transfer current to or from armature.

Conductor: A material through which an electric charge is readily transferred.

Conductance: Ability to conduct electricity.

Ampere:

• The current due to flow of charge at the rate of one coulomb per second.
• The current which when flowing through two parallel wires, separated by a distance of one meter from each other gives rise to a force per unit length on each wire equal to 2x10(-7) N/m.

Ampere-turns: Number of turns of a coil carrying current times the number of amperes flowing.

Electron: Smallest unit of negative electric charge.

Electrolyte: A substance whose solution conducts an electric current.

Electronic current: The current due to flow of electrons.

Conventional current: The current due to flow of an equivalent positive charge.

Eel: Any of various snakelike fishes of the genus, members of which spend most of their lives in fresh water but breed in warm deep oceans.

Valence electrons: Electrons in the outermost shell of an atom that are involved in chemical changes.

Drift: To move along under the force.

Drift velocity: The velocity gained by free electrons in an electrical conductor upon the application of electric field; it is of the order of 10(-3) m/s.

Thermal motion: The motion due to heat energy.

Chemical energy: The kinetic and potential energies of electrons in a chemical compound.

Mechanical energy: Energy transmitted by a machine; energy in the form of mechanical power; the kinetic plus potential energy, if there is no frictional loss.

Heat energy:

• A form of energy associated with molecular motion.
• The energy that flows between a system and its environment by virtue of a temperature difference between them.

Solar energy: The energy produced by nuclear fusion in the sun and comprises almost entirely electromagnetic radiation.

Electrical energy: Energy resulting from the position of an electric charge in an electric field.

Hydal energy: Electricity produced from water power by the arrangement of machinery.

Tidal energy: Electricity obtained from the power plant that uses the ‘head’ of water created

by the rise and fall of the ocean tides to spin the water turbines.

Nuclear energy: The energy liberated by a nuclear reaction (fission or fusion) or by radioactive decay.

Electric arc: A luminous electrical discharge with a high current density, occurring between two electrodes.

Electric Cell (or Cell): A device which converts chemical energy into electrical energy. Combination of two metals or a metal and carbon with an electrolyte to generate an electric current.

Battery: A group of electric cells.

Leyden jar: A glass jar coated on its inner and outer surfaces with a conducting material. An early type of capacitor.

Electrolyte: A substance whose solution conducts an electric current.

Electric generator: An electromechanical device that converts mechanical energy into electrical energy.

Thermo-couples:

• Two dissimilar metallic conductors joined at their ends.
• Junction of two dissimilar metals, in which an emf is generated by reason of a temperature difference.

Solar cell: A device which converts solar energy or artificial light into electrical energy.

Standard cell: A voltaic cell whose e.m.f. is used as a standard.

Circular coil: A long coil of insulated wire wound on a circular support.

Solenoid: A long helically wound coil of insulated wire.

Toroid: A solenoid wound on a circular support instead of a straight one.

Sulphuric acid (H2 SO4 ): A highly corrosive dense oily acid, that is a strong oxidizing agent and is much used in the chemical industry.

Electrolysis: The conduction of electricity through a solution of an electrolyte or through a fused ionic compound, together with the re

Electrolyte: A substance whose solution conducts an electric current.

Electrode: Conducting element in an electric cell, electronic tube, or semi-conductor device.

Anode: The positive electrode or plate of an electronic tube.

Cathode: The negative electrode of an electronic system.

Voltameter: Former name of coulombmeter.

Coulombmeter: An instrument in which the electrolytic action of a current is used for measurement of the quantity of electricity passing through a circuit.

Electroplating: Depositing metal by means of an electric current.

Electrochemical equivalent: The mass of an element in grams, deposited by one coulomb of electricity.

Faraday: The quantity of electricity (96,500 coulombs) required to deposit one chemical equivalent of an element.

Chemical equivalent: The quantity of an element expressed in grams, equal to the ratio of its atomic weight to its valence.

Ohm’s law:

• The potential difference is proportional to the current, provided there is no change in the state of the conductor.
• The ratio of the emf applied to a closed circuit to the current through the circuit is a constant.
• An electric current varies directly as the electromotive force and inversely as the resistance.

Resistance: The opposition to the flow of the electricity.

Resistivity (or Specific resistance): The resistance of a sample of material having specified dimensions.

Ohm: The unit of electric resistance in MKS system; one volt per ampere.

Ohmic: Describing a substance or circuit component that obeys Ohm’s law.

Ohm’s law: The current ( I ) in a conductor is proportional to the potential difference ( V ) between its ends. This leads to, V = IR, where R is the conductor’s resistance.

Potential difference: The work done per unit charge as a charge is moved between two points in an electric field.

Semiconductor (or Semiconductor device): A material such as silicon or germanium, that has resistivity midway between that of conductors and that of insulators.

Semiconductor diode: A semiconductor device, either based on semiconductor junction or on point contact, with two electrodes.

Series arrangement: The arrangement in which the components are arranged to provide a single conducting path for current.

Parallel arrangement: The arrangement, in which two or more components are connected across two common points in the circuit so as to provide separate conducting paths for the current.

Series resistances: Resistors are said to be in series if these are connected such that there is only one conducting path through them.

Parallel resistances: Resistors are said to be in parallel when each one of them is connected across the same two points.

Resistivity: The resistance of a sample of material having specified dimensions.

Specific resistance: The resistance of a sample of material having specified dimensions.

Conductance: Ability to conduct electricity.

Mho: The unit of electrical conductance; the reciprocal of the ohmic resistance.

Siemens (S): The SI unit of electrical conductance, defined as the conductance of an element that possesses a resistance of one ohm. The unit used to be called mho or reciprocal of ohm.

Lattice: A regular periodic repeated three-dimensional array of points that specify the positions of atoms, molecules or ions in a crystal.

Temperature coefficient ( α ): The change in resistance per degree change in temperature per ohm at a particular temperature.

Resistance: The opposition to the flow of the electricity.

Thermometer resistance: A thermometer that measures temperature by the change in electrical resistance of a conductor.

Nichrome: A heat resistant alloy with high resistivity that is used in electrical heating elements and resistors. The composition varies but is approximately 62% Ni, 15% Cr and 23% Fe.

Eureka: An alloy of copper and nickel used for electrical filament and resistance wire.

Ceramics: Inorganic materials, such as pottery, enamels, and refractories.

Tolerance: The allowable range of deviation from the nominal value of an attribute.

Manganin: An alloy of 15-25% Mn, 70-86% Cu, and 2-5% Ni, that has a high electrical resistivity and low temperature coefficient of resistance. It is used for electrical resistances.

Rheostat: A variable resistor for regulating electric current.

Potential divider (or Voltage divider): A number of resistors, inductors, or capacitors connected in series with several terminals at intermediate points.

Potentiometer: An instrument for measuring electrical potential differences by balancing two opposing potentials so that no current flows through a galvanometer. .

Thermistor: A semiconductor device that has a large negative temperature coefficient of resistance, and can be used for temperature measurement, or as a controlling element in electronic control circuits.

Circuit breaker: Device other than a fuse which automatically opens an overload electric circuit.

Ampere:

• The current due to flow of charge at the rate of one coulomb per second.
• The current which when flowing through two parallel wires, separated by a distance of one meter from each other gives rise to a force per unit length on each wire equal to 2x10(-7) N/m.

Electrical power: Rate at which energy is expended or work is done. It is measured in watts.

Potential difference: The work done per unit charge as a charge is moved between two points in an electric field.

Emf (or Electromotive force):

• A measure of the energy supplied by a source of electric current.
• The energy per unit charge supplied by a source of electricity.
• The potential difference between the terminals of a battery or cell when it is
• not supplying current to an external circuit.

Terminal potential difference: The potential difference between the terminals of a battery or cell when it is not supplying current to an external circuit.

Electrical circuit: A combination of electrical components that form a conducting path.

Circuit element: A resistor, capacitor, inductor, transistor, or other device used in making up electric circuits.

Active elements: Those which are capable of delivering power to some external device; such as, voltage and current sources.

Passive elements: Which are capable only, of receiving power; They do not have any source within them.

Electrical network (or Network): A combination of electrical components that form a closed conducting path.

Complex network: Series and parallel combinations of different circuit elements along with many voltage sources.

Branch: In a certain network, each resistor is said to constitute a branch.

Node: A junction of two or more branches is said to be a node.

Reference node (or Datum node): In a network, the junction of the maximum number of branches.

Loop (or Mesh): A closed electrical circuit.

Kirchhoff’s First Rule: The sum of all the currents flowing toward a node is equal to the sum of all the currents flowing away from the node.

Kirchhoff’s Second Rule: The algebraic sum of voltage changes around a closed circuit or a loop must be equal to zero.

Wheatstone Bridge: A circuit, consisting of four resistances connected in such a way so as to form a mesh, used for accurate measurement of electrical resistance.

Wheatstone: Sir Charles Wheatstone (1802-75), English physicist; to designate things invented by or associated with Wheatstone

Post office box: A box containing resistances that can be switched into the circuit, suitable for use as a Wheatstone bridge or potentiometer.

Potentiometer: An instrument for measuring electrical potential differences by balancing two opposing potentials so that no current flows through a galvanometer. .

Galvanometer: An instrument used to measure minute electric currents.

Voltmeter: A meter used for measuring potential differences.

Digital voltmeter (DVM): A voltmeter that displays the measured values as numbers composed of digits.

Cathode ray oscilloscope (CRO): A device used to display input signal into waveform.

Potentiometer: The work done per unit charge as a charge is moved between two points in an electric field.

Potential divider: A number of resistors, inductors, or capacitors connected in series with several terminals at intermediate points.

Aurora: Effect of electric glow discharges observed in the upper atmosphere.

Aurora borealis: Northern lights; seen in the north of the Northern Hemisphere, e.g. it can be seen in Canada.

Written By: Asad Hussain