In a strain gauge, the increase in resistance 
depends on the increase in length 
. The variation of with is shown in the graph below.
The strain gauge is connected into a circuit incorporating an ideal operational amplifier (op-amp), as shown in the figure below.
The strain gauge is initially unstrained with resistance 
. Use data from the graph above to calculate the increase in length of the strain gauge that gives rise to a potential of 
at point A in the figure above.
.
