Test: Kirchoff's Laws

Kirchhoff's Current Law or KCL, states that the “total current or charge entering a junction or node is exactly equal to the charge leaving the node as it has no other place to go except to leave, as no charge is lost within the node“. In other words the algebraic sum of ALL the currents entering and leaving a node must be equal to zero, I_(exiting) + I_(entering) = 0. 

In accordance with Kirchhoff’s second law i.e. Kirchhoff’s voltage law (KVL), the algebraic sum of all the potential differences in a closed electric circuit or closed loop that contains one or more cells and resistors is always equal to zero.
This law is popularly called the law of conservation of voltage.
 

Kirchoff's Law states that the algebraic sum of currents at a junction of an electric circuit is zero. ... Wheatstone bridge is formed by connecting a battery B or an electric source, a plug key K and a variable resistor X between the junctions A and D and a galvanometer G between the junctions C and D.

Minimum possible resistance can be found in a parallel arrangement and maximum possible resistance can be found in a series arrangement.
Thus, 1/R_min=1/R+1/R+....+ n times
=n/R
⇒R_min=R/n
and R_max=R+R+.......+ n times
⇒R_max=nR
∴R_min/R_max=(R/n)/nR=1/n²

When two cells are conneted in parallel , then

Effective Voltage,V = V1 − V2 = 1.25 − 0.75 = 0.5 V