formulas of electricity

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THIS CONTAINS DIFEREENT FORMULAS WITH RELEVANT INFORMATION ON ELECTRICITY

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Slide 1: 

NAME = DEEPAK SHARMA PRESENTATION ON ELECTRICITY CLASS X B

Introduction : 

Introduction Electricity is one of the forms of energy and it can be produced from othertypesof energy, such as the energy of a chemical reaction or of mechanical rotation of a dynamo. Its great advantages are : - Cleanness Flexibility Efficiency Easier transmission over long distance

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Unlike charges attract each other. Equal charges repel each other The force between two charges varies directly as the product of two charges and inversely as the square of the distance between them. Electric charge is conserved i.e. it can neither be created nor be destroyed. Electric charge is additive i.e. total charge is the algebraic sum of the individual charges. Electric charge is quantised and the quantum of charge (i.e. the minimum charge which is capable of free existence) is equal to that on an electron. PROPERTIES OF ELECTRIC CHARGE

ELECTRIC CURRENT : 

ELECTRIC CURRENT An electric current is defined as the ordered motion of electric charge. or Electric current is defined as the rate of flow of electric charge i.e., electric current is the quantity of charge flowing per unit time. I = Q t Q = It UNIT OF CURRENT The SI unit of current is called an ampere (A) in honour of french scientist Andrie Mare Ampere. 1 A = 1C/s AMPERE Current flowing through a conductor is said to be one ampere if one coulomb of charge flows through it in one second.

ELECTRIC POTENTIAL AND ELECTRIC POTENTIAL DIFFERENCE : 

ELECTRIC POTENTIAL AND ELECTRIC POTENTIAL DIFFERENCE ELECTRIC POTENTIAL :- The electric potential energy per unit time is said to be electric potential. electric potential= electric potential energy charge ELECTRIC POTENTIAL DIFFERENCE :- Electric potential difference between two points A and B on a conductor through which a current is flowing is defined as the amount of work done to move a unit charge from A to B. V = W Q W = QV

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A source of electric power (a battery or an AC source), loads and switches and other element connected together by wire from an electric circuit . ELECTRIC CIRCUIT

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R CONNECTING WIRE WIRES JOINED WIRE CROSSING (WITHOUT JOINING) RESISTANCE BOX Components of electric circuit G V A RESISTOR VARIABLE RESISTOR RHEOSTAT ELECTRIC CELL BATTERY OPEN KEY CLOSED KEY GALVANOMETER VOLTAMETER AMMETER

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OHM'S LAW If physical conditions like temperature etc. of a conductor are kept unchanged, the strength of current flowing through it is directly proportional to the potential difference across its ends. This statement is known as OHM’S LAW. V=RI

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RESISTANCE The resistance of a conductor is the ratio of the potential difference across its ends to the strength of the current flowing through it. UNIT:- The SI unit of resistance is known as ohm. The resistance of a conductor is said to be one ohm if a current of one ampere flows through it when a potential difference of one is applied across its ends. R = V I

Classification of material on the basis of Resistivity : 

Classification of material on the basis of Resistivity On the basis of resistivity . Material is divided into four parts. CONDUCTORS:- Metals like copper, aluminium, silver, platinum etc . Have a large number of free electrons and as such posses small resistivity which increases their temperature . SEMI CONDUCTORS:- These posses a very few electrons and as such posses greater resistivity as compared to conductors . The resistivity of semiconductors decrease with temperature . INSULATORS:-These have practically no free electrons and as such have a very high resistivity which decreases with rise in temperature. SUPERCONDUCTORS:-These are material whose resistivity becomes zero below a certain temperature , called critical temperature.

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COMBINATION OF RESISTORS Resistors in series A number of resistors are said to be connected in series if these are joined end to end and the same current flows through each one of them when a potential difference is applied across the combination. The following points are worth to be noticed in case of series combination of resistors If n resistors ,each of value R, are connected in series , their equivalent resistance (RS) is given by RS = R + R + ….. n times = n R The current flowing through each resistor is the same and is equal to the total current in the circuit because there is no other path along which the current can flow. The potential difference across the ends of the combination is distributed across the ends of each one of the resistors. The potential difference across any one of the resistors is directly proportional to its resistance

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Resistors in parallel A number of resistors are said to be connected in parallel If one end of each resistors is connected to one point and the other end is connected to another point so that the potential difference across each resistor is the same and is equal to the applied potential difference between the two points. The following points are worth to be noticed in case of parallel combination of resistors If n resistors ,each of value R, are connected in parallel , their equivalent resistance is given by 1 = 1 + 1 + 1 + ……..n times = n RP R R R R The potential difference across each resistor is the same and is equal to the potential difference across the combination. The main current divides itself and a different current flows through each resistor . The maximum current flows through the resistor with minimum resistance and vice- versa. Connecting a number of resistors in parallel is like providing an equal number of paths for the electron flow which results in a decrease in resistance.

Slide 13: 

Heating effect of electric current Whenever current is passed through a conductor, it becomes hot after sometime. This means that electric energy is being converted into heat energy. Electric bulbs, heater etc. are some of the appliances which are based on this effect ,called the heating effect of electric current It is to be noticed that :- The greater the number of electrons flowing per second , the greater will be the number of collisions and greater the heat produced. The heat produced also depends on the resistance of the conductor which determines the difficulty with which the electrons flow. If the current is passed for a long time, more collisions take place between the electrons and the ions and hence more heat is produced . In 1841 James Prescott Joule (1818-1889) experimentally studied the heating effect of an electric current and came to the conclusion that the amount of heat produced (H) when a current, I flows through a conductor of resistance , R for a time ,t is given by H I2 Rt This relation is called the Joule Law of Heating.

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Electric energy The total work done by a current in an electric circuit is called an electric energy. W = H = VLT = I2 RT = V2 t R Electric Power The rate at which work is done by an electric current is called electric power. P = V I

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Commercial unit of electric energy The electric energy consumed when an electric appliance of power one kilowatt works for one hour is called one kilowatt hour. Thus, 1 kWh = 1kW x 1h = (1000W) x (3600 s) = (1000 J/s) x (3600 s) ( 1 W = 1J/s) = 3.6 x 106 J = 3.6 MJ 1 kWh = 3.6 MJ

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