(a)[3]
With a labelled diagram, describe the arrangement of a metal-wire strain gauge.
(b)
In a strain gauge, the rise in resistance $\Delta R$ depends on the rise in length $\Delta L$. The way $\Delta R$ varies with $\Delta L$ is shown in Fig. 7.1.
(b(i))[3]
The strain gauge is initially unstrained and has resistance $300.0\,\Omega$. Use the data in Fig. 7.1 to calculate the increase in length $\Delta L$ of the strain gauge that produces a potential of $+2.00\,\text{V}$ at point A in Fig. 7.2.
(b(ii))[4]
The strain gauge experiences a further increase in length beyond the value in (b)(i). State and explain which one of the light-emitting diodes, X or Y, will be lit.