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CBSE Class 12-science Answered

kirchoffs law  
Asked by ਰਿਆ ਜੈ | 17 Jan, 2018, 09:54: AM
answered-by-expert Expert Answer
(1) Kirchoff's first law( Current law  or junctin law)
The algebraic sum of electric currents at any junction is always equal to zero.
 
sign convention:- the current flowing towards the juction is positive and current flowing away from the junction is negative.
 
In the figure I1 - I2 + I3 - I4 + I5 = 0
 
(2) Kirchoff's 2nd law ( Voltage law or loop theorem)
In a closed loop of electrical network, the algebraic sum of potential differences for all components plus the algebraic sum of all E.M.F.s is equal to zero.
 
sign convention:-
while tracing a circuit
(i) if the direction of tracing is same as that of the conventional current flow then potential difference across the resistance is considered as negative otherwise it is positive.
(ii) E.M.F. is positive if we traverse from negative terminal to the positive terminal inside the cell and e.m.f is negative if we traverse from the positive terminal to the negative terminal.
 
 
for the figure if we consider the loop ABCDA,  - I1× R1 - E2 - I3 × R2 - I4×R3  + E1 =0 
 
Hence E1 - E2 = I1 × R1 + I3 × R2 + I4 × R3
 

Answered by Thiyagarajan K | 17 Jan, 2018, 11:53: AM

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