Combination of resistance: Various resistances can be combined to
form a network mainly in two ways: (i) Series Combination (ii) Parallel
combination.
In series combination, the
equivalent resistance is equal to the sum of the resistances of individual
conductors. (R= R₁ + R₂ + …. Rn)
In parallel combination the
reciprocal of equivalent resistance is equal to the sum of the reciprocal of
individual resistances.
(⅟₂ = 1/R₁ + 1/R₂ +…. + 1/R n)
Electric Power: The rate at which electrical energy is consumed in
a circuit is called electric power. Its SI unit is watt.
Kilowatthour: It is the unit of energy and is equal to the energy
consumed in the circuit at the rate of 1 kilowatt (1000 J /s) for 1 hour.
1 kilowatt hour = 3.6 x 10⁶ joule
1 k Wh is also called board of
trade unit.
Ammeter: Ammeter is a device which is used to measure electric
current in a circuit. It is connected in series in the circuit.
The resistance of an ideal ammeter
is zero.
Voltmeter: Voltmeter is a device used to measure the potential
difference between two points in a circuit. It is connected in parallel to the
circuit.
The resistance of an ideal
voltmeter is infinite.
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