Q1) Do electrons go first and only after they reached the other side the current appears? Or does the current appear first and it is the reason electrons start to move in the first place?
Q2) Is this the case for lightning too? If so, does it mean there is the current that goes from Earth to thunderclouds?
In: Physics
Scientists originally made the mistake of believing by in current was caused by positive charges moving. This was a mistake, negative charges are the ones.
So positive current really means electrons flow the other way.
Current is defined as negative electron flow. There is no first, current flows or doesn’t.
This all works similarly with lightning, though I believe the clouds can become either positively or negatively charged, so current flow can happen in either direction.
The electron flow is what causes current. The only reason it’s backwards is because we labeled positive and negative when we first observed electricity, before we knew about electrons.
The movement of electrons causes current. Current is literally the rate of electrons flowing. Electrons start flowing instantly as soon as a path is made. Electron flow itself is quite slow, but the whole circuit starts flowing as soon as a path is made.
Lightning strikes are typically actually a few transmissions of electrons back and forth between the ground. Electrons tend to flow both ways.
Let me know if I need to clarify anything or if you have subsequent questions.
Contrary to the other responses, current does not cause the flow of electrons. Current IS the flow of electrons. It does not cause itself.
**Voltage** is what causes electrons to flow. Voltage induces current. (Hence the equation V = IR, voltage equals current times resistance.)
Voltage is when the two ends of a conductive “wire” attach to two substances with very different electric charges (potential, really). For instance, the negative terminal of a battery has a much more negative electric charge than the positive terminal of the battery. When you attach the two ends of a wire to the two terminals of a battery, the strong negative electric charge in the negative terminal will push on the electrons in the wire, and the strong positive charge in the positive terminal will pull on the electrons in the wire, nudging them down the wire towards the positive end. That movement is the current.
Electrons go “backwards” in a positive current because electrons are negatively charged, and the current is positive. It’s just nomenclature. It makes more sense to define a positive current as positive charges moving forward, because current can refer to the flow of positive charges as well. Thus, positive charges more forward in a positive current, and negative charges move backwards in a positive current.
(Edit: Like, consider if electrons had positive charge. Then they would be drawn towards the negative terminal of the battery and pushed away by the positive terminal. So they would flow the opposite direction if they had opposite charge. The direction positive charges will flow in a circuit is defined as the positive values of current.)
The reason for conventional current being positive to negative is because we discovered electricity long before we discovered the electron and have just stuck with it since. Doesn’t really impact anything important.
For an electric current to flow you need two things a potential difference and a resistance to connect the two. A potential difference is a difference between two or more energy levels, for example if you stood on the first floor of a building you’d have more potential energy than someone on the ground floor and we call that difference the potential difference or 1 volt if it was electricity rather than gravity. Some one on the second floor would have 2 volts relative to the ground and 1 relative to the first floor etc.
A resistor is something that connects two potential differences. If we have two pools of water side by side no water will flow between the two unless we have a potential difference and a connection between the two. So we could raise one tank up and put a hose between the two and bingo bango we have a water current that we could use to power something. The water started flowing as soon as the connection was made.
But hang on that won’t continue indefinitely. Either the top tank will run out of water or the bottom tank will fill up. So we could connect both to a pump that will send water back to the higher tank and complete our water circuit. That’s our power supply.
Q.2 lightning is a bit more complicated. Lightning is actually a change of state from a gas to a plasma, in the same way water changes state from ice to well water. I usually describe this process through a dinner party wedding event but don’t really have the time right now to go through it in full. But essentially a really large voltage exists between clouds and ground that causes a thing called electrical breakdown. When this happens the lightning is able to make a path to ground, it doesn’t follow the path of least resistance it actually makes a path of lower resistance.
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