The algebraic sum of the electric currents meeting at the common point is_________

• A. One
• B. Negative
• C. Infinity
• D. Zero

Answer: (D)

Kirchhoff’s Current Law (KCI ) or Kirchhoff’s Junction Rule. This law is based on the conservation of charge and may be stated as under:
The algebraic sum of the currents meeting at a junction in an electrical circuit is zero.
An algebraic sum is one in which the sign of the quantity is taken into account. For example, consider four conductors carrying currents I1, I2, I3, & I4 and meeting at point O as shown in Fig
 
If we take the signs of currents flowing towards point O as positive, then currents flowing away from point O will be assigned negative sign. Thus, applying Kirchhoff’s current law to the junction O we have,
(I1) + ( I2) + (−I3) + (−I4)  = 0 or(I1) + ( I2) = (−I3) + (−I4)
i.e., Sum of incoming currents = Sum of outgoing currents.
Therefore, Kirchhoff’s current law may also be stated as under:
The sum of currents flowing towards any junction in an electrical circuit is equal to the sum of currents flowing away from that junction. Kirchhoff’s current law is rightly called the junction rule.
Kirchhoff’s current law is true because electric current is merely the flow of free electrons and they cannot accumulate at any point in the circuit. This is in accordance with the law of conservation of charge. Hence, Kirchhoff’s current law is based on the law of conservation of charge.