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Chapter- 12, , dHH, , Electricity, Charge is a fundamental particle in an atom. It may be positive or negative., , Like charges repel each other., Unlike charges attract each other., , Coulomb (C): S. I. unit, , of charge, , I Coulomb charge = Charge present on approx. 6x 10" electrons, , Charge on 1 electron= Negative charge of 1.6 x 10-"C, , Q=ne, Where, , Q=Charge (total), n=, , No., , of electrons, , e= Charge on I electron, Current (1): The rate of flow of charge is called, , current, , Current= Charge, Time, , S. I. unit, , of current= Ampere (A), 1A=1 Cs, I mA=10A, , IuA= 10-*A, Current is measured by Ammeter. Its symbol is, , A

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Ammeter has low resistance and always connected in series., Direction of current is taken opposite to fow of electrons as electrons were not know, at the time when the phenomenon of electricity was discovered first and current wa, , considered to be flow of positive, , charge, , Potential Difference (V): Work done to move a unit charge from one point to another., , I Volt: When l joule work is done, V=, , n carrying one Coulomb charge, , then potential diference is called, volt., , S.I. unit of Potential diftierence = Volt (V), , V=1 JC, 1 Volt: When l joule work is done in, is called 1 volt., , carryingone Coulomb charge then potential differenc, , Voltmeter: Instrument to measure potential difference., T t has high resistance and always connected in parallel. Symbol is, , Cell is the simplest device to maintain potential difference., Current always flow from higher potential to lower potential., , Symbols of Some Commonly Used Components in Circuit, Electric cel, , HHE, , Battery, Key (open), Key (closed), Wire joint, Wire, , Crossing (without join), , Electric bulbb, , or, , Resistance, , www., , Rheostat, , wwwW- orWWW, , Ammeter, Voltmeter, Science Class (SA-)-X, , A, , V-

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Ohm's Law: Potential difference across, , directly proportional, , to current, , the, , two, , through, , passing, , points of a, , the circuit, , metallic conductor is, , provided, , that, , temperature, , remains constant., , Mathematical, , expression for QOhm's law:, VI, V=IR, , R is, , a, , constant called resistance for, , a, , given metal., , VI graph for Ohm's law:, , Current (), Resistance (R) : It is the property of a conductor to resist the flow of charges through it., Ohm (2): S., , I. unit ofresistance., , 1 ohm = v o l t, 1ampere, , When potential diference is 1 Vand current through the, circuit is 1 A, then resistance is I ohm., , Rheostat: Variable resistance is a component used to regulate current without changing, the source of, , voltage., , Factors on which the Resistance of a Conductor depends :, , Resistance of a uniform metallic conductor is, , 0) directly proportional to the length ofconductor,, (i) inversely proportional to the area of cross-section,, (nikdirectly proportional to the temperature and, (iv)depend on nature of material., Resistiv ity (P): t is defined as the resistance offered by a cube of a material of side, m when current flows perpendicular to its opposite faces., I t s S.I. unit is ohm-metre (Qm)., , Electricity

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Resistivity, , does not, , with, , change, , in, , change, , length, , or area, , of cross-section but, , changes with change in temperature, , Range of resistivity, , Range, , of metals and, , alloys is 10, , of resistivity of insulators is 10, , to, , 10, , to, , 10* Am., , 2m., , Resistivity of alloy is generally higher than that of its constituent metals, Alloys do not oxidize (burn) readily at high temperature, so they are commonlyused in electrical heating devices., , Copper and aluminium, , are, , used for electrical transmission lines, , as, , they, , have low., , resistivity, , Resistors in Series:, w** ww., , R, , LHHH, When two, , or more, , resistors, , are, , connected end to end, the, , arrangement is called series, , combination., , Total/resultant/overall/effective resistance in series, , R R, +R+R,, , Current, , through, , Equivalent, , each resistor, , resistance is, , is same., , larger than, , the, , largest, , individual resistance., , Total voltage = Sum of voltage drops, , V=V,+V, +V,, Voltage, , across, , each resistor, , V, IR,, , V,=IR, V, = IR,, , V= IR, + IR, + IR,, , IR=I(R, +R, +R,), R R, +R, tR,, Science Class (SA-)-X, , IV,+V, +V, =V], V=IR

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Resistors in Parallel:, R, , wwwy, ww, , Voltage across each resistor is sanme and equal to the applied voltage, Total current is equal to sum of currents through the individual reistances, , I=+1,+1,, v_VVV, RRRR, Reciprocal of equivalent resistance is equal to sum of reciprocals of individual, , resistances., , L-L,L,1, , R, R, R R,, , Equivalent resistance is less than the value of the smallest individual resistance in the, combination., Advantages of Parallel Combination over Series Combination, (i) In series circuit, when one component fails, the circuit is broken and none of the, , component works, (ii) Different appliances have different requirement of curent. This cannot be satisfied in, series as current remains same., (1in)The total resistance in a parallel circuit is decreased., , Heating Effect of Electric Circuit, If an electric circuit is purely resistive, the source of energy continually get dissipated, entirely in fom of heat. This is known as heating effect of electric current., As, , Or, , VIr, Heat produced. H= Vi, Heat produced, H, , E=PxT, , =, , E =H}, {V=IR}, , FR, , Joule's Law of Heating Efect of Electrie Current, It states that the heat produced in a resistor is, , Electricity

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(i) directly proportional to square of current, H, (i) directly proportional to resistance for a given current, H, , (ini)directly proportional, , to, , time for which, , current, , flows, , R, , through the conductor,, , H, , 1., , H-FRI, , 0,, , Heating, , effect is desirable in, , devices like electric heater, electric iron, electric bulb,, , electric fuse, etc., , Heating, , effect is undesirable in devices like, , computers, computer, , monitors (CRT),, , TV, refrigerators etc., In electric bulb, most of the power consumed, small part of it is radiated in form of light., , Filament, , of electric bulb is made up of tungsten, , by, , the filament appears, , a, , heat and, , a, , as, , (i) it does not oxidise readily at high temperature., , (i) it has high melting point (3380° C), chemically, prolong the life of filament, , The, , bulbs, , Electric Fuse, , are, , :, , It is, , filled with, , a, , safety, , inactive gases like, , device that protects, , our, , electrical, , nitrogen, , appliances, , and argon, , in, , case, , to, , of short, , circuit or overloading., , Fuse is made up of pure tin, , always connected in, Fuse has low melting point., Fuse is, , or, , alloy, , of copper and tin., , series with live wire., , Current capacity of fuse is slightly higher than that of the appliance., Electrie Power:, , The, , rate at which, , electric energy is consumed, , or, , dissipated, , circuit, P=VI, , P-FR=R, S.I. unit of power = Watt (W), , 1 Watt= I volt x I ampere, , Commercial unit otf electric energy, , = Kilo Watt hour (KWh), , I KWh=3.6x 10°J, , 1 KWh= l unit of electric energy, Science Class (SA-)- X, , in, , an, , electric

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QUESTIONS, VERY SHORT ANSWER TYPE QUESTIONS (1 Mark), 1., , Define S.I. unit, , of, , (a) Electric current, (b) Potential difference, (c) Resistance, (d) Electrice power, (e) Electrical energy consumed, 2, , Define the term, , 3, , Device used for measuring the current is.., , resistivity., ., , 4. Name the element of filament ofa bulb., 5. Write two types of resistors combination., SHORT ANSWER TYPE QUESTIONS (2, I., , How the voltmeter and ammeter are connected in a circuit?, , 2, , Why the filament of bulb has high melting point ?, , Marks), , 3.How does fuse wire protect electrical apliances ?, 4, , Find the number of joules in 1 KWh., , 5., , Find, , 6., , On what factors does resistance of a conductor depend?, , a, , relationship between P, I and V, SHORT ANSWER TYPE QUESTIONS (3 Marks), , State Ohm's law Derive relation between 1, V and R. Draw the graph between V and, 2. What is Joule 's heating efect of curent P ? Derive its expression., , 3, , What would be, , 4., , Find the effective resistance between A andB., , new, , resistance if, , length, , of conductor is doubled and thickness is, , halved ?, , Electricity

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12, , I2, , wwww., , wwww., , 12, , 12, www., , www12, , wwwww, , 12, , wwwww, , wwwww, , 30, 7, , S2, ww., , wwwM, , wwww, , 32, , 3S2, , 22, wwww, 252, , 292, , 22, 292, www, , 3, , 5., , connect lights and other appliances in domestic wir, , Which is the better way, and why ?, , LONG ANSWER TYPE QUESTIONS (5 Marks), ., , Explain the, in, , 2., , In, , a, , Joule's law of, , conductor, , depends, , heating., , How and, , on, , what factors does the heat, , ?, , the circuit given below, calculate, 42, www., , 22, wwww., , HH, 652, (a) Total effective resistance, , (b) Potential difference, 3., , Three resistances of, , across, , 42, 20., , 20, 30 and 5Q are connected, , Science Class (SA-D-XX, , in electric circuit. Find, , produc

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(a) maximum effective resistance., , (b) minimum effective resistance., 4, , On what factors, the resistance of, , a, , conductor, , expression. Give the SI unit of resistivity., , depends, , ? Give the mathematical, , VALUE BASED QUESTION, That, , right Vinay, , preparing, , for his science exam. Suddenly light of his room went off, His cousin brother Vasu quickly with mobile, phone torch found that fuse has blown., He checked and put a fuse wire. The, light come to life again., thanked Vasu and, was, , Vinay, , continued his study., (a) What, , was, , the values, , displayed by Vasu and Vinay, , ?, , (b) What is electric fuse?, (c) What characteristics you would, Hints, , 1. H=PRTT, , 2, , Factors: Current,, (a) Total, , to, , prefer for a fuse wire ?, Long Answer Type Questions, , Resistance, Time., , effective resistance, 40+20= 62, 111-3, R 32, , (6), , V, V, , 3, , (across 40)= IR =1 x4=4V, (across 20)= IR= 1, x2, , 2V, , (a) R= 100, , (b) R=, , Electricity