2. Introduction
Today you will learn what resistance
is, and how it can be useful in
electrical appliances, some factors
affecting resistance and how to work
out the resistance of a component by
measuring the current and voltage
across it.you will also get to know
some special resistors, and their
uses
3. Resistance
Resistance is the opposition that an electrical device
has to the flow of electrical current.
All devices have some resistance.
A resistor is a device that has a particular resistance.
7. Text
Fixed Resistors
These resistors have a fixed resistance in order to control the size of
currents and voltages.Resistors are included in circuits so that the
correct voltage is applied across the bulb and the correct current flows
through it.
8. Text
Variable Resistors
These resistors have different resistance and it's possible to
alter their resistance.when you alter the volume of television or
speed of a fan you use a variable resistor to do so
10. Diodes
Diodes are resistors that
direct the flow of current
in one direction.
Used in rectifier circuit
to convert AC to DC.
11. Thermistors
A resistor whose resistance
changes with the temperature
Resistance of a thermistor⬇️
as the temperature⬆️
Eg:Temperature sensors in
fire alarms
High Temperature
Low Temperature
I
V
12. Light Dependent Resistors
(LDR)
A resistor whose
resistance depends on
light intensity
Resistance of a LDR⬇️ as light
intensity⬆️
Eg:Photographic equipment,
automatic lighting control, some
garage, gates
I
V
Bright light
Low light
13. Ohm's Law
The current that flows
through a conductor is
directly proportional to
the potential difference
across its ends,provided
its temperature remains
constant.
Obey's Ohm's Law
Doesn't Obey Ohm's Law
