(a)[2]
Calculate the potential $V^+$ at the non-inverting input of the op-amp.
(b)[2]
At $10\,^{\circ}\text{C}$, the thermistor has a resistance of $2.5\,\text{k}\Omega$. State and explain whether the light-emitting diode (LED) is emitting light.
(c)[2]
Explain why the student’s circuit will not show any change in temperature above $0\,^{\circ}\text{C}$.
(d)[3]
The resistor with resistance $5.0\,\text{k}\Omega$ is replaced by a resistor of resistance $R$ so that the LED switches on or off at a temperature of $20\,^{\circ}\text{C}$. Determine $R$ in k$\Omega$.