(a)[2]
Calculate the potential $V^+$ at the op-amp’s non-inverting input.
(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 cannot show any change in temperature for values above $0\,^{\circ}\text{C}$.
(d)[3]
The $5.0\,\text{k}\Omega$ resistor 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 $\text{k}\Omega$.