Question

Kirchoff’s junction law is equivalent to
A. Conservation of energy
B. Conservation of charge
C. Conservation of electric potential
D. Conservation of electric flux

Answer 1

Hint: Kirchoff’s junction law is also known as Kirchoff’s current rule, states that the algebraic sum of all the current meeting at a junction in a closed circuit is always zero. And kirchhoff's current rule supports the conservation of change.

Complete step by step answer:

To solve the complicated electric circuits, Kirchoff proposed two rules. These rules are an expression of conservation of election change and energy.
This rule is known as junction rule or current rule which states that the algebraic sum of current meeting at junction in a closed electric circuit is zero.
$\sum I=0$
Sign convention: Current flowing in conductor towards the junction is taken as positive and the current flowing away from the junction is taken as negative.
To demonstrate this rule, let us consider current\[{{I}_{1}}\], \[{{I}_{2}}\], \[{{I}_{3}}\], \[{{I}_{4}}\] and \[{{I}_{5}}\] as shown in figure.

\[{{I}_{1}}\], \[{{I}_{2}}\] and \[{{I}_{3}}\]approaches towards the junction, therefore, these are positive current.
\[{{I}_{4}}\] and\[{{I}_{5}}\] moving away from the junction, therefore, these are negative current.
\[\begin{align}
  & \sum I=0 \\
 & {{I}_{1}}+{{I}_{2}}+{{I}_{3}}-{{I}_{4}}-{{I}_{5}}=0 \\
 & {{I}_{1}}+{{I}_{2}}+{{I}_{3}}={{I}_{4}}+{{I}_{5}} \\
\end{align}\]
Hence, it follows the conservation of charge, as electric current is nothing but rate of flow of electric charge.
Therefore, option B. is correct.

Additional Information:
Kirchoff’s second rule is voltage rule or loop rule: It states that the sum of potential difference across all elements including the EMF’s around any closed circuit is equal to zero.
i.e. \[\sum EMF+\sum V=0\]
This law is based on the law of conservation of energy.

Note: To implement Kirchoff’s first rule i.e. junction rule quickly, at any junction just do the sum of incoming current equals to sum of outgoing current.
In implementing voltage rule or kirchhoff's second rule select a closed loop in any circuit and for sign convention: In direction of current take the sign of potential difference as negative because current flows from high potential to low potential, opposite to direction of current take potential difference as positive.