Advertisements
Advertisements
Question
State Kirchhoff's rules and explain on what basis they are justified.
Advertisements
Solution
Kirchhoff’s first rule (Junction rule): The algebraic sum of the currents meeting at a point in an electrical circuit is always zero.
\[\sum_{} I = 0\]
This law is justified on the basis of law of conservation of charge.
Kirchhoff’s second law (Loop rule): In a closed loop, the algebraic sum of the emfs is equal to the algebraic sum of the products of the resistances and the current flowing through them.
\[\sum_{} I = 0\]
This law is justified on the basis of law of conservation of energy.
APPEARS IN
RELATED QUESTIONS
State the two Kirchhoff’s rules used in electric networks. How are there rules justified?
Determine the current in each branch of the network shown in figure.
Determine the equivalent resistance of networks shown in Fig.
An infinite ladder is constructed with 1 Ω and 2 Ω resistors, as shown in the figure. (a) Find the effective resistance between the points A and B. (b) Find the current that passes through the 2 Ω resistor nearest to the battery.
Two unequal resistances, R1 and R2, are connected across two identical batteries of emf ε and internal resistance r (see the figure). Can the thermal energies developed in R1 and R2 be equal in a given time? If yes, what will be the condition?
In the circuit shown in the figure below, E1 and E2 are two cells having emfs 2 V and 3 V respectively, and negligible internal resistance. Applying Kirchhoff’s laws of electrical networks, find the values of currents l1 and I2.
Twelve wires each having a resistance of 3 Ω are connected to form a cubical network. A battery of 10 V and negligible internal resistance is connected across the diagonally opposite corners of this network. Determine its equivalent resistance and the current along each edge of the cube.
State Kirchhoff ’s voltage rule.
State the principle of potentiometer.
Obtain the condition for bridge balance in Wheatstone’s bridge.
How the emf of two cells are compared using potentiometer?
Kirchhoff’s second law is a consequence of law of conservation of ______.
Assertion: Kirchhoff’s junction rule follows from conservation of charge.
Reason: Kirchhoff’s loop rule follows from conservation of momentum.
The Kirchhoff's second law (ΣiR = ΣE), where the symbols have their usual meanings, is based on ______.
While measuring the length of the rod by vernier callipers, the reading on the main scale is 6.4 cm and the eight divisions on vernier is in line with marking on the main scale division. If the least count of callipers is 0.01 and zero error - 0.04 cm, the length of the rod is ______.
Three resistors having resistances r1, r2 and r3 are connected as shown in the given circuit. The ratio `"i"_3/"i"_1` of currents in terms of resistances used in the circuit is :
In a meter bridge the point D is a neutral point (Figure).
- The meter bridge can have no other neutral point for this set of resistances.
- When the jockey contacts a point on meter wire left of D, current flows to B from the wire.
- When the jockey contacts a point on the meter wire to the right of D, current flows from B to the wire through galvanometer.
- When R is increased, the neutral point shifts to left.
The value of current in the 6Ω resistance is ______.
The figure below shows two batteries, E1 and E2, having emfs of 18V and 10V and internal resistances of 1 Ω and 2 Ω, respectively. W1, W2 and W3 are uniform metallic wires AC, FD and BE having resistances of 8 Ω, 6 Ω and 10 Ω respectively. B and E are midpoints of the wires W1 and W2. Using Kirchhoff's laws of electrical circuits, calculate the current flowing in the wire W3:
