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# Current Electricity: Summary

Physics : Current Electricity: Summary

SUMMARY

┬Ę        The current, I flowing in a conductor I = dQ/dt ,where dQ is the charge that flows through a cross-section in a time interval dt. SI unit of current is ampere (A). 1A = 1 C s-1.

┬Ę        The current density J in a conductor is the current flowing per unit area. J = /AI

┬Ę        Current is a scalar but current density is a vector.

┬Ę        The general form of OhmŌĆÖs law ┬Ę        Practical form of OhmŌĆÖs law states that V ŌłØ I, or V = IR where I is the current.

┬Ę        The resistance R of a conductor is R = V/I .  SI unit of resistance is ohm (╬®) and 1 ╬® = 1V/1A

┬Ę        The resistance of a material R = Žü l/A where l is length of the material and A is the area of cross section.The resistivity of a material determines how much resistance it offers to the flow of current.

┬Ę        The equivalent resistance (RS) of several resistances (R1, R2, R3ŌĆ”ŌĆ”..) connected in series combination is RS = (R1+R2 +R3ŌĆ”ŌĆ”..)

┬Ę        The equivalent resistance (RP) of several resistances (R1, R2, R3ŌĆ”ŌĆ”..) connected in parallel combination is  1/RP = 1/R1 + 1/R2 + 1/R3 ŌĆ”ŌĆ”ŌĆ”ŌĆ”ŌĆ”ŌĆ”, ┬Ę        KirchoffŌĆÖs first rule (Current rule or junction rule): The algebraic sum of the currents at any junction is zero.

┬Ę        KirchoffŌĆÖs second rule (Voltage rule or loop rule): In a closed circuit the algebraic sum of the products of the current and resistance of each part of the circuit is equal to the total emf included in the circuit.

┬Ę        Electric power is the rate at which energy is transformed.

┬Ę        If a current I flows across a potential difference V, the power delivered to the circuit is P = IV.

┬Ę        In a resistor R, the electrical power converted to heat is P = I2R =V2/R

┬Ę        The energy equivalent of one kilowatt-hour (kWh) is 1kWh = 3.6 X 106 J.

┬Ę        Metre bridge is one form of WheatstoneŌĆÖs bridge.

┬Ę        Potentiometer is used to compare potential differences.

┬Ę        JouleŌĆÖs law of heating is H = VIt (or) H = I2Rt.

┬Ę        Thermoelectric effect: Conversion of temperature differences into electrical voltage and vice versa. Tags : Physics , 12th Physics : Current Electricity
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