Page 417 - Physics Coursebook 2015 (A level)

Chapter 25: Electronics
13 In order to switch on a heater when the temperature falls below a set value, a potential divider is connected to a switching circuit. When the input voltage to the switching circuit falls below 0.5 V, it switches the heater on.
to potential divider
Figure 25.32 For End-of-chapter Question 13.
a Copy Figure 25.32 and add a suitable potential divider circuit to trigger the switching circuit. [2]
b Explain how the operator could lower the temperature at which the heater is switched on. [1]
14 Figure 25.33 shows a circuit used to monitor the variation of light intensity in a room.
X
a Identify the component X and describe how the circuit works. [3]
b Suggest the reason for including the variable resistor in the circuit. [1]
switching circuit
V
Figure 25.33 For End-of-chapter Question 14.
405