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G.B.N GOVT. POLYTECHNIC NILOKHERI SUBJECT:- PHYSICS BY:- PHYSICS FACULITIES

Learn about electric current, types, Ohm’s Law, resistance, specific resistance, series & parallel combinations of resistances, conductance, heating effect of current, and superconductivity. Explore the world of electricity!

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G.B.N GOVT. POLYTECHNIC NILOKHERI SUBJECT:- PHYSICS BY:- PHYSICS FACULITIES

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  1. G.B.N GOVT. POLYTECHNICNILOKHERISUBJECT:- PHYSICSBY:- PHYSICS FACULITIES

  2. CURRENT ELECTRICITY ELECTRIC CURRENT The rate of flow of electric charge is called electric current. If ‘Q’ is the charge that passes through any conductor in time ‘t’ then current I=Q/t 1Amp=1C/1s

  3. CURRENT ARE OF TWO TYPES:- • 1. DIRECT CURRENT- If the magnitude and direction of the current remains constant at all time interval and graph between current and time is a straight line. Then, the current is known as DIRECT CURRENT.

  4. 2. ALTERNATING CURRENT- If the magnitude and direction of the current changes continuously at regular interval of time and graph between current and time is a sin or cosine curve then the current is known is ALTERNATING CURRENT.

  5. OHM’S LAW • According to ohm’s law the current flowing through a conductor is directly proportional to the potential difference applied across the ends of the conductor provided physical conditions remains same. • V α I • Or V=IR Or R=V/I • This constant is called resistance of conductor.

  6. RESISTANCE • It’s the property of a material due to which it opposes the flow of electric current through it. • Unit of resistance is ohm and it’s denoted by (Ω)

  7. Factors upon which resistance of a conductor depends are the following:- • It’s proportional to the length of the conductor. R α l -(1) • It’s inversely proportional to the area of cross-section of the conductor. R α 1/a -(2) • It depends upon the nature of material. • It depends upon the temperature.

  8. SPECIFIC RESISTANCE • Specific resistance of a material of a conductor can be defined as the resistance offered by a conductor of a material having length of 1m and area of cross section 1m square. • S.I. Unit of specific resistance is Ωm. • By combining (1) and (2) • R α l/a • R=S.l/a • If l=1, a = 1 • Then R=P (P is called rho)-(3)

  9. Series Combination of Resistances:-Two or more resistances when connected in series have Constant current and varying voltage. Therefore the total voltage is the sum total of individual voltages V= V1+V2+V3

  10. PARALLEL COMBINATION OF RESISTANCES:-Two or more Resistances when connected in parallel have constant voltage and varying current.Therefore the total current is equal to the sum total of individual currents

  11. CONDUCTANCE • It’s the property of a material to permit electric charge to flow through it. Therefore, conductance is the reciprocal of resistance. • It’s denoted by ‘G’ , G=1/R • S.I Unit = mho/m.

  12. Heating Effect of Current • Whenever an electric current passes through a conductor then the conductor will become hot. This heating effect is known as joule’s heating. • Also, heat produced will depend upon the square of the current passing through the conductor and the time taken in which the current is passing through the conductor. • H=square of current×Resistance×time.This law is known as joule’s law of • heating

  13. SUPERCONDUCTIVITY • It’s the phenomena in which the conductor has zero resistance at very low temperature .This phenomena is known as superconductivity.

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