A student designs a circuit incorporating an operational amplifier (op-amp) as shown in the figure below.
State the purpose of this circuit.
The resistors X and Y each have resistance 
. When conducting, the LED labelled B emits blue light and the LED labelled G emits green light.
State whether blue light or green light is emitted when the resistance of component C is greater than the resistance 
of the variable resistor. Explain your answer.
State and explain what is observed as the resistance of component C is reduced.
. Therefore, the output of the amplifier is negative, and hence, only the green light is emitted.
. Therefore, the output of the amplifier is positive, and hence, the green light goes off and the blue light comes on.
