Question

In a Wheatstone bride all the four arms have equal resistance R. If the resistance of galvanometer arm is also R, the equivalent resistance of combination is

• A. 2R
• B. R/4
• C. R/2
• D. R

Answer 1

The correct option is D R

As all the four arms have equal resistance R so it is a balanced (P/Q=R/S) Wheatstone bridge circuit. Thus, no current flow in the galvanometer arm and its resistance will not working. So the corresponding circuit is shown in figure.
The equivalent resistance is $R_{AB}=\frac{(R+R)(R+R)}{(R+R)+(R+R)}=4R^2/4R=R$