Question : (i) The current I1 in a wire is getting divided in two wires with currents I2 and I3 at a junction in a circuit.The currents in the three wires are related by I1 = I2 + I3.
(A) State the fundamental law from which this relation is derived.
(B) Explain the validation of law of conservation of energy in Kirchhoff's voltage law?
(II) How the balancing condition gets affected if you are interchanging the galvanometer and the cell in the Wheat stone bridge?
CBSE Sample Question Paper 2025
Solution :
(i)
(A) This relation is the mathematical form of Krichhoff's First Law / Kirchhoff's Current Law. This is derived from the fundamental "Law of Conservation of Charge".
(A) This relation is the mathematical form of Krichhoff's First Law / Kirchhoff's Current Law. This is derived from the fundamental "Law of Conservation of Charge".
(B) As per the KVL, the sum of all the emf in a closed loop is equal to the sum of the product of current and resistances in it, which is equivalent to the statemement that the sum total of energy remains cosntant, it can neither be created not be destroyed. Hence, Kirchhoff's voltage law (KVL) is validate by law of conservation of energy.
(ii) In a wheatstone bridge the balance condition is given by
P/Q=R/X (When Ig=0)
The position of galvanometer and cell in a wheatstone bridge is symmetrical. The balacing condition depends on the ratio of the resistance and not on the position of the galvanometer and cell.
P/Q=R/X (When Ig=0)
The position of galvanometer and cell in a wheatstone bridge is symmetrical. The balacing condition depends on the ratio of the resistance and not on the position of the galvanometer and cell.
Hence, the balacing condition will not get affected when the position of galvanometer and cell is interchanged.