Recently, we’ve been studying electricity at school and one thing I’m incredibly confused about is voltage. When I try to find explanations, I find people using analogies to give a basic idea but actually not explain what it is?
So far, I believe that Voltage acts like a pushing force force the current to flow. Is this correct? or Is there anything I’m missing.
In: Physics
A voltage is a difference in potential energy. It measures the amount of energy it takes to move a particle with an electric charge from one point in space to another. Moving a positively charged particle from a lower voltage to a higher one requires energy, and moving it back down releases energy. For a negative charge like an electron, this is reversed – going up in voltage releases energy.
There is a fundamental force in our universe that physically pushes positive particles towards negative ones, and this accelerates the particle, giving it kinetic energy. Voltage is a measure of how much energy is gained due to this force when a given amount of charge moves from one specific point in space to another. This is why 1 Volt is one Joule (measure of energy) per Coulomb (measure of charge).
As an example, if I allow one electron to flow from one side of a 1.5V battery to the other, I have moved -1.602×10^(-19) coulombs through 1.5 joules per coulomb. Multiplying these values gives you an amount of energy, and this is the kinetic energy gained by the electron as it moves.
As an aside, this is why voltage is always measured between two points in space. E.g. between two sides of a battery, between two charged plates, or between a live wire and the ground beneath it. A single point does not have a voltage, only a voltage relative to a specific other point.
The best analogy in my opinion is actually gravity. If I lift a heavy object up onto a table, this is akin to moving a positive charge up to a higher voltage. If the object is allowed to fall from the table, it will gain kinetic energy as it moves down. You could say the object doesn’t like being at a greater height, and it “wants” to move down. A positive charge “wants” to go down in voltage, too.
Like charge repel, opposite charge attract. If you put a small charge, called test charge, in an environment with other charges, it will experience force. Let’s say you make all the charges have a fixed position and only let the test charge move, and try to move test charge from point A to point B, you will have to oppose against this force, and this cause you to expend energy, ie. do work. This amount of work is increase with the amount of charge of the test charge. The rate of change between work done over charge at 0 charge is called the potential difference between point A and point B, also known as the voltage.
This electric “potential difference” is exactly the electric analog of gravity potential difference. In gravity, potential difference is the also the rate of change of work done to move an object against gravity, over the mass of the object, at 0; and gravitational potential is just potential difference compared to a fixed reference point, like the ground.
(ignore magnetic force in this discussion)
So, imagine electricity like water in a rubber hose. Wattage is the volume of water. Amperage is how wide the hose needs to be to allow for the water to flow at that rate. And voltage is the amount of pressure behind it.
Of course, amperage changes when the wattage goes up or down. More volume needs a bigger channel. But also, changing the voltage will change the amperage. If you use more pressure on the hose, the channel becomes smaller.
Electrical charges like to be in some places more than others. When the move from a place they like less toward a place they like more, they accelerate, doing work. Unsurprisingly (but it pays to spell these things out explicitly), the places that positive charges like are the same places negative charges dislike, and vice versa.
The way we quantify this being-liked-by-electric-charges characteristic of places is with a concept called *electric (or electrostatic) potential.* Its units are volts.
>So far, I believe that Voltage acts like a pushing force force the current to flow.
In a way.
Think of a hydroelectric dam; the amount of power that dam can create at any given time is dependent on the flow-rate of water through the dam and the height of the dam (and thus the difference in potential energy caused by gravity wanting to pull all that water down to sea level. In electricity, amperage is analogous to the flow-rate, and voltage is analogous to the height of the dam.
Voltage is like height with gravity.
With gravity if you have a height difference, things (with mass) will generally try to fall from the higher one to the lower one. You have to put in energy to lift something up to a higher height, and you get out energy when things fall down to a lower height.
Voltage – or potential difference – is the electricity version of height (almost). If you have a 9V potential difference between two points in a circuit, current will flow from the higher p.d. to the lower one (obviously the electrons will go the other way, thanks charge convention).
The bigger the potential difference the more energy you will get out when the current drops between them.
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Voltage, or potential, is a bit of a weird concept because it doesn’t exist in any real sense, which is why we have to use analogies. It is a mathematical tool to help understand how things work.
Potential can be defined in a couple of ways, either as the amount of energy needed to move a thing of unit charge between the two points, or it can be defined in terms of the underlying (force) field.
voltage is the potential difference between two points. the amount of “pressure” that would be there if you connected them, if you allow flow. one of those points has a higher charge than the other and voltage is how we describe that difference.
i have never liked the pressure analogy because electricity isn’t pushed, if anything it is pulled, like water flowing downhill. the measure of how steep the hill is would be the voltage, but it is still only potential until we say how much water (amps). so then the energy of how steep the hill and how much water together would be watts (volts X amps).
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