WEBVTT

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let us talk about superposition theorem

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an electrical circuit does not always
contain a single source of supply

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it may contain more than one source of supply. the
sources of supply may be either voltage sources

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or current sources, or both voltage, and current sources

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there is a special type of circuit solving method for
such circuits that contain more than one source of supply

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here, the effect of each source is calculated separately, and the
combined effects of all the sources are taken into consideration

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here, the effect of each source on a particular
branch of a network is calculated first separately

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then, we have to add all effects
on that branch of the circuit

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the sum of the effects gives the actual effect on the
branch when all the sources are acted on the circuit

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the superposition theorem states that in a
linear network containing more than one source

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the current flowing in any branch is the algebraic sum of currents
that would have been produced by each source taken separately

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with all the other sources replaced by their respective internal resistances. in case, the
internal resistance of a source is not provided, the voltage sources will be short-circuited

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and current sources will be open-circuited. to
clarify the concept, let us take an example

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using the superposition theorem

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let us find the value of current,
in the branch BD in the circuit

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we shall consider each source separately, and
calculate the current flowing through the branch BD

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for that, first the 24 volt source is taken by
short-circuiting the 12 volt source, as shown here

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now, by applying any simple circuit law, we will find
that the current through the branch BD is, 4 by 3 ampere

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now, consider the 12 volt source, and
short-circuit the 24 volt source as shown

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now, by applying any simple circuit law, we will find
that the current through the branch BD is, 2 by 3 ampere

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sum of these two currents would be
4 by 3 plus 2 by 3, that is 2 ampere

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after, taking both sources into circuit. let
us calculate the current through the branch BD

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by applying any simple circuit law, we will find
that the current through the branch BD is, 2 ampere

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so, it is proved that, the current flowing through the branch is the algebraic sum of currents that would have been
produced by each source taken separately, with all the other sources replaced by their respective internal resistances

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this is superposition theorem.
hope, you got the concept. thank you