Hey guys,
I'm slowly making my way through the first chapter of the All About Circuits book (awesome awesome stuff) and want to try and get my understanding of electron flow fairly solid.
What I'm not sure about at the moment is why current stays the same through all parts of a simple circuit. Here's my understanding so far, it'd be great if someone could clarify or point out where I'm going wrong/missing something:
Take a simple circuit with just a battery and a resistor connected to the battery. In my minds eye, this is how I visualise it from reading the first chapter of the book (sorry if this is a bit long but I'm trying to clarify things )
- Voltage is the force that moves electrons between two inequally charged atoms until they're equally charged. This is because on the one hand, the excess electrons in one atom are being attracted to the protons in the other atom, while the other atom doesn't have enough electrons itself to push the new electrons from the first atom away. The stronger the imbalance, the stronger the force within the electric field to make the electrons balance out (is this because more electrons have to move if the balance is to be equalled out?).
- A group of electrons moving in unison is a current. To measure a current, you count the number of electrons passing a single point over a certain amount of time (say one second). The more electrons that pass the point during that time, the stronger the current.
Now here is the first point I'm not sure about. My impression is a resistor is harder to push electrons through than a wire. Do the electrons slow down as they go through the resistor, coming out the other end slower? If this is the case, is it because the resistor is causing 'friction' which converts some of the electron's voltage into heat (instead of ALL the voltage being converted into electron movement)? Is this the same as saying the resistor actually applies a 'reverse voltage' to the electrons flowing through it, essentially?
Now the electrons come out the other end and go through the battery. My next question (and I think I might have the answer to it, but I'm not sure) is why does the current remain constant through the circuit?
If I was to guess what was happening, I've got two expectations from my understanding. One is that the electrons get pushed through the battery quickly, then slow down at the resistor. So you'd get a higher measurement of current if you measured at a point between the negative terminal of the battery and the resistor and a lower measurement of current if you measured at a point after the resistor as the electrons were on their way back to the positive terminal of the battery.
However, I realise this impression doesn't take into account that all the electrons in a circuit are affecting their neighbours (touching each other, so to speak). Taking this into account, my guess is what actually happens is that there are two opposing forces acting on ALL the electrons in the circuit. The first one is the voltage supplied by the battery, that makes the electrons want to move forward. The electrons moving forward push the other ones in front of them forward, giving the ones in front their voltage and moving together as a current. On the other hand, at the same time, the resistor is trying to push the electrons back in the direction they are arriving. This force is being transferred backward through all the electrons, which causes them all to slow down (even making them move slower through the battery). Since everything is linked together, the resistance causes the current to drop through the whole circuit.
Now my final question, if this is right, what happens to the current inside the battery? Do the electrons inside the battery move slower, or does the battery try and move them through itself at the same speed (which I gues would cause a pileup of electrons at the negative terminal of the battery)?
Hopefully I haven't bored you all to death. I know my intuitive understanding is probably wrong in a few places, would be nice to hear your feedback
I'm slowly making my way through the first chapter of the All About Circuits book (awesome awesome stuff) and want to try and get my understanding of electron flow fairly solid.
What I'm not sure about at the moment is why current stays the same through all parts of a simple circuit. Here's my understanding so far, it'd be great if someone could clarify or point out where I'm going wrong/missing something:
Take a simple circuit with just a battery and a resistor connected to the battery. In my minds eye, this is how I visualise it from reading the first chapter of the book (sorry if this is a bit long but I'm trying to clarify things )
- Voltage is the force that moves electrons between two inequally charged atoms until they're equally charged. This is because on the one hand, the excess electrons in one atom are being attracted to the protons in the other atom, while the other atom doesn't have enough electrons itself to push the new electrons from the first atom away. The stronger the imbalance, the stronger the force within the electric field to make the electrons balance out (is this because more electrons have to move if the balance is to be equalled out?).
- A group of electrons moving in unison is a current. To measure a current, you count the number of electrons passing a single point over a certain amount of time (say one second). The more electrons that pass the point during that time, the stronger the current.
Now here is the first point I'm not sure about. My impression is a resistor is harder to push electrons through than a wire. Do the electrons slow down as they go through the resistor, coming out the other end slower? If this is the case, is it because the resistor is causing 'friction' which converts some of the electron's voltage into heat (instead of ALL the voltage being converted into electron movement)? Is this the same as saying the resistor actually applies a 'reverse voltage' to the electrons flowing through it, essentially?
Now the electrons come out the other end and go through the battery. My next question (and I think I might have the answer to it, but I'm not sure) is why does the current remain constant through the circuit?
If I was to guess what was happening, I've got two expectations from my understanding. One is that the electrons get pushed through the battery quickly, then slow down at the resistor. So you'd get a higher measurement of current if you measured at a point between the negative terminal of the battery and the resistor and a lower measurement of current if you measured at a point after the resistor as the electrons were on their way back to the positive terminal of the battery.
However, I realise this impression doesn't take into account that all the electrons in a circuit are affecting their neighbours (touching each other, so to speak). Taking this into account, my guess is what actually happens is that there are two opposing forces acting on ALL the electrons in the circuit. The first one is the voltage supplied by the battery, that makes the electrons want to move forward. The electrons moving forward push the other ones in front of them forward, giving the ones in front their voltage and moving together as a current. On the other hand, at the same time, the resistor is trying to push the electrons back in the direction they are arriving. This force is being transferred backward through all the electrons, which causes them all to slow down (even making them move slower through the battery). Since everything is linked together, the resistance causes the current to drop through the whole circuit.
Now my final question, if this is right, what happens to the current inside the battery? Do the electrons inside the battery move slower, or does the battery try and move them through itself at the same speed (which I gues would cause a pileup of electrons at the negative terminal of the battery)?
Hopefully I haven't bored you all to death. I know my intuitive understanding is probably wrong in a few places, would be nice to hear your feedback