Edexcel IGCSE Physics 复习笔记 2.2.5 Electrical Components
Edexcel IGCSE Physics 复习笔记 2.2.5 Electrical Components
Thermistors
A thermistor is a temperature-dependent resistor
It is represented by the following circuit symbol:
Thermistor circuit symbol
The resistance of a thermistor changes depending on its temperature
As the temperature increases the resistance of a thermistor decreases and vice versa
The resistance through a thermistor is dependent on temperature
LDRs
A light-dependent resistor (LDR) represented by the following circuit symbol:
LDR circuit symbol
The resistance of an LDR changes depending on the light intensity on it
As the light intensity increases the resistance of an LDR decreases and vice versa
The resistance of an LDR is dependent on the amount of light intensity on it
Lamps illuminate (light up) when a current flows in a circuit
LEDs are types of diodes
This means they only allow current to pass in one direction through them and will only light if the current passes in that direction
LEDs also illuminate when a current flows in a circuit (provided the LED is placed in the correct direction)
Since both electrical components have a visual response to current, they can be used to indicate the presence of a current in a circuit
LEDs can be used to indicate the presence of a current, because they illuminate when current flows through them. The same is true for lamps
Make sure you learn the various symbols mentioned on this page. Many of them are very similar with small differences denoting what they do:
Two arrows pointing towards a symbol mean that it is light-dependent
Two arrows pointing away mean that it is light-emitting
Symbols are sometimes drawn with circles around them (e.g. the LDR). These circles are often optional (although not in the case of meters and bulbs).
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