(a)[3]
Describe the structure of a metal wire strain gauge. You may include a diagram if you want.
(b(i))[1]
The operational amplifier (op-amp) is ideal. The circuit output potential $V_{\text{OUT}}$ is given by $V_{\text{OUT}} = \frac{R_F}{R} \times (V_2 - V_1)$. State the term used for the ratio $\frac{R_F}{R}$.
(b(ii))[3]
The strain gauge S has resistance $125\,\Omega$ when it is unstrained. Calculate the size of $V_1$ so that, when strain gauge S is not under strain, the output $V_{\text{OUT}}$ is zero.
(b(iii))[2]
In one test, the resistance of S rises to $128\,\Omega$. $V_1$ remains the same. The ratio $\frac{R_F}{R}$ is 12. Calculate the size of $V_{\text{OUT}}$.