Page 50 - Physics_Form_2

Physics for Secondary Schools

Types of resistors Variable resistors
A resistor is an electrical component These are resistors whose electric resistance
with two terminals used to restrict the can be adjusted (from zero to its maximum
flow of electric current in a circuit. That value) to suit the requirements of a circuit.
is, resistors control the magnitude of the Examples of variable resistors include
current in a circuit in accordance with rheostats, voltage dividers, thermistors,
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Ohm’s law. There are two basic types of photoresistors and magneto-resistors. Some
resistors depending on their applications types of variable resistors and their circuit
and characteristics. These are fixed symbols are shown in Table 2.5.
resistors and variable resistors.
Table 2.5: Variable resistors and their
Fixed resistors symbols
The most commonly used type of resistor Appearance of a Symbol
is the fixed resistor. A fixed resistor has a resistor
constant value of resistance. Applications
of fixed resistors include protecting
electrical components from excess
current, dividing voltage in a circuit, and
controlling the working of some circuits.
In a circuit, the fixed resistor is represented Photoresistor
by the symbols shown in Figure 2.8.

Thermistor

f
Figure 2.8: Circuit symbols for fixed resistors

Diverse resistor materials are used to Force resistor
fabricate fixed resistors. These materials
influence the resistor’s properties, such as
tolerance and noise. Fixed resistors can
be made of carbon, wound wire, metal Magneto-resistor
oxide and metal films.

Task 2.2

Use library or online resources Potentiometer
to outline characteristics, internal
structure, and applications of carbon,
wound wire, metal oxide and metal
films resistors. Rheostat

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Student’s Book Form One

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