(a(i))[1]
State the name of an electrical sensing device that reacts to a change in length.
(a(ii))[1]
State the name of an electrical sensing device that reacts to a change in pressure.
(b)[4]
A relay is sometimes chosen as the output of a sensing circuit. The output from one such sensing circuit is either $+2\,\text{V}$ or $-2\,\text{V}$. On Fig. 10.1, add symbols for a relay and any other required component so that the external circuit turns on only when the sensing circuit output is $+2\,\text{V}$.