- Why do birds sitting on High tension line; not getting Electrical shock ?
- What are Phase & Neutral ?
- Why there are multiple pins on single phase plug ? OR Why do minimum two terminals required to run an Electrical System ?
- Why do we get electrocuted from a single potential wire while standing on Earth ?
All these questions have one single answer that is “Potential Difference” !
“An image of single phase socket 230VAC-6Amps been shown above which is having three holes. Right down hole contains phase; left down hole contains neutral While the middle bigger hole represents Earthing ! ”
|
|
POTENTIAL DIFFERENCE
|
|
Potential difference or Voltage difference is “Actually the voltage/potential difference between two nodes.” For the working of the load, Current should flow through the load & Current only will flow when there is potential difference across the load. That’s why potential difference is the Mandatory to run an Electrical System !
LETS UNDERSTAND THE POTENTIAL DIFFERENCE THROUGH AN EXAMPLE
“Let suppose, There are two tanks; Tank 1 & Tank2. Both are interconnected from the bottom. At initial, Tank 1 is full(High Potential) with water & Tank 2 is empty(zero potential).
Due to the positive pressure on tank 1; Pressure flows from Tank 1 to Tank2. A flow meter connected in between both the tanks shows the water flow(current flow).
Water flows from Tank1 to Tank2; Until both the tanks get levelled. Flow get stop only when both the tanks get leveled means there is no net potential difference. This is the similar phenomenon works in Electrical system.”
IMPORTANT TERMS RELATED TO POTENTIAL DIFFERENCE
“Every individual node has its potential with respect of zero(ground). Even for the Potential measurement of a single node, A secondary node; ground is needed.”
Potential is AC or DC, That’s also matters. Because DC power is scalar quantity while AC is vector quantity. Potential difference between two different nodes in Which both the nodes have some potential with respect to ground, Produces entirely different potential difference which depend upon the magnitude & phase angles between the nodes.
Some important terms related to potential difference for both the supplies discussed below:
- Phase is the potential which is having the type of Alternating quantity Whose magnitude Continuously moving changing with respect to time.
- Neutral is the type of return path for alternating quantity which is generated from its source; Generally originated from the mid point of Y-connections. Neutral may contains some sort of potential which depend upon the winding configuration of the source & load balancing across the phases of the source.
- Ground is the zero potential also known as earthing; type of sink. Ground conductor is buried into the Earth.
- Positive(DC) is the potential & type of Direct quantity; Which remains constant throughout the time.
- Negative(DC) is the zero potential which is created from the circuitry. Negative provides return path to direct current.
|
|
A GIF below shows the pure DC waveform; Moving with respect to time at constant rate without any deviation, without any change in direction.
|
|
A GIF of AC sinusoidal waveform which is moving with respect to time but changing its direction at fixed intervals.
|
|
PRACTICALLY MEASURING THE POTENTIAL DIFFERENCE
Potential difference between Phase & Neutral
Potential difference between phase & neutral known as per phase voltage.
Phase Voltage= 238V AC
Neutral=0
Per phase voltage(Vpn)=238-0=228V AC
|
|
Potential difference between Phase & Ground
An accurate working ground contains zero potential than difference between phase & ground becomes;
phase=228V AC
Vpe=228-0=228V AC
Potential difference between two phases
Since phase is alternating quantity whose potential depend upon the angle & magnitude. Potential difference between two phases is not a type of arithmetic sum Instead it is a type of phasor sum Which is also known as line voltage.
For example
(3 phase polyphase system of sinusoidal nature)
Phase1 Voltage with respect to neutral=228V AC
Phase2 Voltage with respect to neutral=228V AC
In three phase polyphase system; 2 phases are 120° apart. Which means phases are not exact opposite to each other.
That’s why it is not true, (Vph-Vph)=228-(-228)=456
Rather, It is Vph-Vph=√3*228= 394.8
|
|
Potential difference between Positive & Negative
In DC power supply, Potential difference actually follows the arithmetic sum, Since it does not contains any phase angle.
For example
Positive=24V DC
Negative=0
Vdc=24-0=24
Positive1=12Volts
Positive2= -12 Volts
Potential difference= 12-(-12)=24VDC
Q&A RELATED TO POTENTIAL DIFFERENCE
Q1. Why do birds sitting on High tension line; not getting Electrical shock ?
Ans. Birds sitting on single high tension line; are not under potential difference. There is only potential; No potential difference which means no current flow across the bird. If some how While sitting on potential wire, Bird touches the another potential/earthing than it will get burnt.
Q2. What are Phase & Neutral ?
Ans. Phase is the potential which is the type of alternating quantity which continuously changes its direction at fixed interval while moving with respect to time. Neutral is a return path for alternating quantity which is generally generated from the mid point of (Y)star-connection.
Q3. Why there are multiple pins on single phase plug ? OR Why do minimum two terminals required to run an Electrical System ?
Ans. Single phase plug contains 3 pins in which 2 pins are phase & neutral which is necessary for the system to get run While 3rd pin is Earthing ; Which generally do not has to do with the working of the system but it ensure safety to us, Earthing terminal make sure device’s metal body remains at zero potential.
Q4. Why do we get electrocuted from a single potential wire ?
Ans. In total discussion we have concluded that for current flow; a potential difference is the Mandatory. Than why do we get electrocuted from a single Phase wire ?
When we get electrocuted after touching the potential; we get a sensation of vibration, Body starts glowing like a bulb, it attracts like a magnet & weakness starts increasing.
What if, When We are in contact with potential BUT we do not get a sensation of vibration, body not glowing, no weakness either than What we will say, We are not electrocuted !
When we get electrocuted from a single potential wire while standing on ground. There is actually the potential difference working across the body & Ground. Ground act as a big sink source. But if some how, if we insulate ourself properly from the ground & only the potential(LT) in our hand than we will not get Electrocuted.
Hope, You like the post. If you have any doubt, suggestion or query please do comments !