resistance

1. Resistance

2. Resistance
Resistance defined as an obstacle to the flow of
electric current.
Is the opposition offered by any object to the passage
of an electric current through it.
Unit: Ohm ( Ω )

3. Resistance Equation
Resistance=Voltage/Current
R=V/I
• Resistance is measured in ohms
• Voltage in volts(V),Current in
amps(I)
• You can rearrange the equation to
find voltage & current
R=V/I
V=R*I
I=V/R

4. Resistors
A resistor is a two-terminal electronic
component that produces a voltage across its
terminals that is proportional to the electric
current through it in accordance with Ohm's
law:
V = IR

5. RESISTOR IN SERIES
The total resistance of resistors in series is equal to
the sum of their individual resistances.

6. RESISTOR IN PARALLEL
If two or more components are connected in parallel they
have the same potential difference (voltage) across their
ends. The potential differences across the components
are the same in magnitude, and they also have identical
polarities. The same voltage is applicable to all circuit
components connected in paralle

7. TextTypes Of Resistors
FIXED RESISTORS.
VARIABLE RESISTORS.
SPECIAL RESISTORS.

8. 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.

9. 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. Text
Special Resistors
Diodes, Thermistor, LDR

11. Diodes
Diodes are resistors that
direct the flow of current
in one direction.
Used in rectifier circuit
to convert AC to DC.

12. 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

13. 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

14. Factors Affecting Resistance

15. Length
Resistance of a conductor is directly proportional
to the length of the wire i.e., longer the wire
greater will be the resistance and shorter the wire
smaller will be the resistance. If L represents the
length of the uniform wire, then
R  L

16. Diameter (Cross-sectional area)
Resistance of a conductor is inversely
proportional to the area of the cross-section of
the uniform wire. That means, thinner the wire,
greater the resistance and thicker the wire,
lower the resistance. If A is the area of cross-
section of the uniform wire, then,

17. Temperature
• The resistance of a metallic conductor
increases as the temperature increases
e.g. copper
• The resistance of a
semiconductor/insulator decreases as the
temperature increases

18. APPLICATION OF
RESISTANCE
The most common applications of large-scale
resistance ,
 automotive industry,
 aerospace industry,
railway industry,
 food and beverage industry,
nuclear industry,
solar industry,
 material handling industry,
 military/defense industry

19. THANK YOU