Page 201 - WCS - Electrical

Basic electricity - Ohm’s law, relation between V.I.R & related problems
Basic electricity - Ohm’s law, relation between V.I.R & related problems
WORKSHOP CALCULATION & SCIENCE - CITS
Exercise 1.7.35
Exercise 1.7.35
Ohm’s law
Ohm’s law
Basic electricity - Ohm’s law, relation between V.I.R & related problems
V - Voltage in volts Exercise 1.7.35
V - Voltage in volts
l l - Current in Ampere
- Current in Ampere
Ohm’s law
R - Resistance in ohms.
R - Resistance in ohms.
In any closed circuit the basic parametres of electricity
V - Voltage in volts
In any closed circuit the basic parametres of electricity
(Voltage, Current and resistance) are in a fixed relationship
(Voltage, Current and resistance) are in a fixed relationship
- Current in Ampere
l
to each other.
to each other.
R - Resistance in ohms.
Basic values
Basic values
In any closed circuit the basic parametres of electricity
To clarify the basic electrical values, they can be compared
To clarify the basic electrical values, they can be compared
(Voltage, Current and resistance) are in a fixed relationship
to a water tap under pressure
to a water tap under pressure
to each other.
Water pressure - electron pressure - Voltage Relationships
Water pressure
- electron pressure
- Voltage
Basic values
Relationships
Amount of water - electron flow - Current
- Current
Amount of water
- electron flow
To clarify the basic electrical values, they can be compared If the resistance is kept constant and the voltage is is
If the resistance is kept constant and the voltage
to a water tap under pressure
throttling of tap - obstruction to - Resistance increased, the current is increased
increased, the current is increased
- Resistance
throttling of tap
- obstruction to
- electron pressure
Water pressure electron flow - Voltage Relationships
I  V
I  V
electron flow
Amount of water - electron flow - Current If voltage is constant and the resistance is increased,
If voltage is constant and the resistance is increased,
If the resistance is kept constant and the voltage is
current is decreased
current is decreased
throttling of tap - obstruction to - Resistance increased, the current is increased
electron flow l  
I  V
l
If voltage is constant and the resistance is increased,
Ohm’s law
current is decreased
Ohm’s law
From the above two relationships we obtain Ohm’s law,
From the above two relationships we obtain Ohm’s law,
l 
which is conveniently written as V = R.I.
which is conveniently written as V = R.I.
Ohm’s law
Ohm’s law
Ohm’s law states that at constant temperature
Ohm’s law states that at constant temperature
From the above two relationships we obtain Ohm’s law,
From the above two relationships we obtain Ohm’s law, which is conveniently written as V = R.I.
the current passing through a closed circuit is
the current passing through a closed circuit is
directly proportional to the potential differ-
directly proportional to the potential differ-
which is conveniently written as V = R.I.
Ohm’s law states that at constant temperature the current passing through a closed circuit is
ence, and inversely proportional to the resis-
ence, and inversely proportional to the resis-
directly proportional to the potential difference, and inversely proportional to the resistance.
tance.
tance.
Ohm’s law states that at constant temperature
the current passing through a closed circuit is
directly proportional to the potential differ-
By Ohm’s law
By Ohm’s law
By Ohm’s law
ence, and inversely proportional to the resis-
tance.
EXAMPLE
EXAMPLE
EXAMPLE
A bulb takes a current of 0.2 amps at a voltage of 3.6 volts.
A bulb takes a current of 0.2 amps at a voltage of 3.6 volts.
A bulb takes a current of 0.2 amps at a voltage of 3.6 volts. Determine the resistance of the filament of the bulb
By Ohm’s law
Determine the resistance of the filament of the bulb to find
Determine the resistance of the filament of the bulb to find
to find R. Given that V = 3.6 V and l = 0.2 A.
R. Given that V = 3.6 V and l = 0.2 A.
R. Given that V = 3.6 V and l = 0.2 A.
EXAMPLE
A bulb takes a current of 0.2 amps at a voltage of 3.6 volts.
To find ‘R’. Given that V = 3.6V and I = 0.2 A
To find ‘R’. Given that V = 3.6V and I = 0.2 A
To find ‘R’. Given that V = 3.6V and I = 0.2 A
Determine the resistance of the filament of the bulb to find
Therefore V = l x R
Therefore V = l x R
R. Given that V = 3.6 V and l = 0.2 A.
Therefore V = l x R
= 0.2 A x R
3.6 V = 0.2 A x R
3.6 V
= 0.2 A x R
3.6 V
To find ‘R’. Given that V = 3.6V and I = 0.2 A
Therefore
Therefore
Therefore
Therefore V = l x R
Example = 0.2 A x R
3.6 V
The voltage supply to a filament lamp is 10.8V. The voltage should be 12V. Find out loss of voltage.(Fig 5)
Therefore
107
107
188
107
CITS : WCS - Electrical - Exercise 18