Name: Meter Bridge
Uploaded: 2019-07-19
Duration: 7 min 2 s
Description: Measurement, by comparison, is always accurate. The video talks about a metre bridge device that helps us find the unknown resistance by comparing it with a...

Question

State Kirchhoff's (i) junction rule and (ii) loop rule.

Accepted Answer

Kirchhoff established the following two laws to study the current flowing in a circuit:

(1) Kirchhoff's first law applies to currents at a junction in a circuit. It states that at a junction in an electrical circuit, the sum of currents flowing into the junction is equal to the sum of currents flowing out of the junction.

The law is based on the conservation of charge where the charge (measured in coulombs) is the product of the current (in amperes) and the time (in seconds). If the net charge in a region is constant,

In the above figure, the current coming into the junction is equal to that going out of it i.e.

$I_{1} + i_{2} = I_{3} + I_{4}$ .

(2) Kirchhoff's second law, also known as Kirchhoff's voltage law (KVL) states that in any complete loop within a circuit, the sum of all voltages across components that supply electrical energy (such as cells or generators) must equal the sum of all voltages across the other components in the same loop. This law is a consequence of both charge conservation and the conservation of energy.

Consider a circuit as shown above, The current distribution is shown according to Kirchoff's first rule. Applying Kirchoff's second rule to the close loop $ABCDEFA$ , we get.,

$- e_{2} + e_{1} = - I_{2} R_{3} + I_{1} R_{1} i . e . ΣE = ΣIR$

Similarly, for the closed path $BEDCB$ $e_{2} = I_{3} R_{2} + I_{2} R_{3}$ .

For closed-loop $ABEFA$

$e_{1} = I_{3} R_{2} + I_{1} R_{1}$

State Kirchhoff's (i) junction rule and (ii) loop rule.

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