(a) Fig. 8.1 is the symbol for a light-emitting diode (LED).
Fig. 8.1
On Fig. 8.1, mark the polarity of the diode such that the diode is emitting light. [1]
(b) Fig. 8.2 is a circuit diagram for a temperature-sensing device.
+9V +9V
+9V
Question
Physics
Edexcel2023
The circuit shown provides an input to a transistor. A transistor is a type of electronic
switch and in this circuit it can be assumed to have infinite resistance.
Question
Physics
Edexcel2023
1 1 10 100 1000
Light level / lux
The transistor switches on when the potential difference across the input increases above
The intensity of light incident on a light dependent resistor (LDR) can vary both its
electrical resistance R and the number of charge carriers per unit volume n. The light
intensity on an LDR is increased.
Which row of the table describes the effect on R and n?
R n
A decreases decreases
B decreases increases
C increases decreases
D increases increases
(Total for Question 7 = 1 mark)
Question
Physics
CAIE2016
(a) The symbol for a light-emitting diode (LED) is shown in Fig. 7.1.
Fig. 7.1
On Fig. 7.1, mark the polarity of the diode such that the diode is emitting light. [1]
(b) The circuit diagram for a temperature-sensing device is shown in Fig. 7.2.
Fig. 7.2
The operational ampli fi er (op-amp) is ideal.
Some values for the resistance of the thermistor at different temperatures are given in Fig. 7.3.
temperature / ° C resistance / Ω