Old but gold!
This is a direct descendant of a page I wrote in 1998.
I thought the material was important then, I still think so.
Anyone can give you a kit of bits and instructions... little more than a recipe for baking a cake. If you ever want to go beyond that, make something new, invented by you, you will need to grasp the following.
The material will also help you diagnose what is wrong when something isn't working.
Before I go on, I'd like to thank Clive Maxfield for his Cool Beans blog, and in particular his page addressing the same issues. (That's where the link will take you.) It reminded me that mine was languishing at an old website, and needed updating!
Current: Electronic and electrical things 'work' because electrons are flowing through them. This is current, abbreviation 'I', measured in amps. The more amps, the hotter, faster, louder, etc it will be. Talking of current is always relative to a single point in a circuit... the number of electrons passing that point. Current 'just happens' whenever you have a circuit.
Voltage: What makes the electrons move. Voltage is always a comparison between two points, but usually one of them is assumed to be the 'zero voltage' point chosen by the person who drew the circuit. Consider a single 1.5 v 'battery'. (More properly called a cell.) If you attach your voltmeter to the two ends of the battery, it will read 1.5 v. If you take a wire from the '+' end, to a light bulb, from there to second light bulb, and from that back to the '-' end of the battery and then get busy with your volt meter, you will discover the following: From + to - is still 1.5 v (if your battery is fresh!) From '+' to the bit of wire between the bulbs is 0.75 v. From the same bit of wire to '-': 0.75 v again. Think of the electrons going around as being like climbing a mountain. The battery has whatever push it takes to get electrons all the way 'round. (You all the way to the top). If the path has obstacles, the push gets broken up as needed. Suppose your mountain has an ice cream seller at the half way point. To get there uses up half the push you have, the rest of the climb takes the other half. Voltage comes from cells, batteries, power supplies. Note that if you connect too little resistance (see next) to a given voltage source, the voltage it is meant to produce isn't supplied... and you may damage things, too.
Resistance. Measured in ohms. Again, resistance is always a measurement of the resistance between two points. It is whatever makes it hard for electrons to go through the circuit. Without resistance, the amount of current from even one volt would be infinite. Anything electricity flows through will have some resistance, though the resistance of wire is too low to be important, generally speaking.
Easy when you know about the big three: If you have a fixed voltage, say 10 volts, then doubling the resistance in a circuit will half the current. Notice that the current is what it is, resulting from the facts of the voltage and resistance involved. To put it mathematically, the current will be the voltage divided by the current. E.g. With a voltage of 10v and a resistance of 100 ohms, the current will be 0.1 amp.
Remember that current is electrons flowing. Imagine your circuit as the Amazon River system. Where the part you are looking at has only one way for the water to get from A to B, the circuit is 'in series'. The light bulbs above were in series. Where the river splits into multiple channels (and rejoins later) the circuit is 'in parallel'. Some circuits, like the Amazon can be a mixture of series bits and parallel bits. If you zoom in on a small part, it can be series or parallel or a mixture.
When the two (or more) branches in a parallel circuit all have the same resistance, the current in each will be the same... a half (or third, etc) of the current 'upstream' of the branch. (The current after the branches rejoin will be the same as the current going in. You don't lose current, even if it may be split between paths.) If one path has twice the resistance of the other, it will have half the current of the other.
Voltage is easy. You generally attach one probe to whatever part of the circuit the designer has called 'zero' volts, and then connect the other probe to the place you want to know about. Remember that even though we talk about the voltage 'at such-and-such a point', implicit is always the second part: 'compared to where we had the other probe.' Negligible amounts of electricity flow through the voltmeter, so you can measure voltages without disturbing the circuit.
Current is a little trickier. You have to 'cut a wire' (literally or effectively, e.g. by disconnecting one from come component of the circuit) and 'bridge the gap' with the ammeter. The ammeter has virtually no resistance, so be careful NOT, for instance, to connect it to the two ends of a battery: Some voltage + very little resistance = a high current, rapidly exhausted battery, and melted ammeter.
Resistance is a real pain. Generally, you have to remove the object of interest from the circuit and attache the ohmmeter probes to the two ends. It applies a voltage to the object, looks at the current which results, and decides from that what the resistance is. Note... transistors are 'non-ohmic' devices... you don't measure their 'resistance'. Neither would you put an ohmmeter on logic gates.
Forget watches. Forget music recording systems. (The words aren't misused in those cases, but the way they are used won't help you here.) In electronics, digital devices are those which, fundamentally, operate on an 'all or nothing' basis. They are 'on' or 'off', e.g. light bulbs (forgetting the possibility of a dimmer 'switch'.) Now... if you have a digital device with several parts, you can take a few 'on/offs' together and have a code with more than two possibilities... but the underlying components can only be 'on' or 'off'.
Analogue, on the other hand is the situation where you have gradations in between 'on' and 'off'. A radio is an analogue device because it can be off, soft, medium, loud, very loud, or outrageous.
If you found this of interest, please mention in forums, give it a Facebook "like", or whatever. If you want more of this stuff: help!? There's not much point in me writing these things, if no one hears about them. Does anyone feel they are of any use? If YOU do- please spread the word!
Search across several of my sites at once with a Google search button.
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Unlike the clever Google search engine, this one merely looks for the words you type, so....
* Spell them properly.
* Don't bother with "How do I get rich?" That will merely return pages with "how", "do", "I"....
Please also note that I have three other sites, and that this search will not include them. They have their own search buttons.
It's both! Flat-Earth-Academy.com is something I started years ago. For a variety of reasons, I can't offer you httpS:// access there. (As you are not asked to input any information, that's moot, but it "worries" search engines.) So I'm moving to my new, all singing, and will do the httpS:// dance site, "WYWTK.com", and Flat-Earth-Academy is gradually acquiring pages there. (Well, HERE, as what you are reading is one of my "wywtk/fea" pages.)
Why "WYWTK"? It comes from "What You Want To Know".
Page has been tested for compliance with INDUSTRY (not MS-only) standards, using the free, publicly accessible validator at validator.w3.org. It passes in some important ways, but still needs work to fully meet HTML 5 expectations. (If your browser hides your history, you may have to put the page's URL into the validator by hand. Check what page the validator looked at before becoming alarmed by a "not found" or "wrong doctype".)
AND tested for
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