Question

A strain gauge with $130\Omega$ resistance and gauge factor of 2.5 is placed in one arm of a symmetric Wheatstone bridge. With bridge supply current of 30 mA the output of the bridge corresponds to 40 units. Under the identical condition if the supply current is increased to 45 mA then the ratio of new output to the old output is?

• A. 2
• B. 0.67
• C. 1.5
• D. 1

Answer 1

The correct option is C 1.5

The bridge output voltage is directly proportional to supply voltage/current.

Hence,

$V_o\propto V_s$

or

$V_o\propto I_s$

$\frac{V_{02}}{V_{01}}=\frac{I_{s2}}{I_{s1}}=\frac{45}{30}$

$\text{Required ratio}\Rightarrow \frac{V_{02}}{V_{01}}=1.5$