Ohms Law

[trash]

I thought it might be of some use to share some basic concepts of eletronics and radio that I and others here have learnt over the years.
I hope the following information is useful to some of you in this hobby and may even help with school and employment in the future.

So here goes …

One of the basic fundamentals of eletronics is called “Ohms Law”.
It is just an official name for how eletricity behaves.
As mentioned elsewhere eletricity in wires behaves a lot like water does in pipes.

The amount of water in the pipe is like the current in a wire.
The more water, the bigger the pipes need to be to carry it. The same is true for electricity and wires. If the wires aren’t big enough, they get hot and melt.
The current is measured in AMPS. An Amp is a rather large unit and most circuits don’t use this much. A single LED uses 20mA.
20 milliamps or 20/1000th’s of an amp. Tiny.

The pressure of water is similar to the voltage of electricity.
You can have water pressure without water flowing, likewise you
can have a voltage between the terminals of a battery even though
there is no current flowing. Increase the pressure behind a tap, eventually it will break. Similarly, increase the voltage across two terminals and it will spark over.
Volts are actually the unit of measurement, the correct name for
voltage is EMF – Electro Motive Force, but nobody really uses that name.
You’re probably pretty familiar with voltages. 1.5V for most simple single cell batteries, 12V for car batteries, 48V on your phone line,
240V in your power points, 415V out on the street, 11000V on the top street wires and 330000 Volts on some high tension wires.

Resistance is the opposition to the flow of current.
The easiest way to think of it is like a thinner water pipe or
a pipe with a choke flange in it. It restricts the amount of water
that gets through.
To get more water through the same narrow pipe, you need more pressure. Likewise if you keep the pressure the same but make the pipe bigger, more water will flow.

More Voltage across the same resistor means more current.
Resistance is measured in OHMS.

The relationship is very simple.
Voltage / Current = Resistance
Voltage / Resistance = Current
Resistance x Current = Voltage

To make 1 amp flow through 10 Ohms requires 10 Volts.

The final piece to the puzzel is called POWER.
Power is measured in WATTS.
It is … Voltage x Current = Power

Looking up at your light globe on the ceiling you’ll probably see
a 60 Watt light globe. The meaning is very simple, this light uses 60W of power. Duh Trash! 😛

Ok, we know that the electricity in our house is 240V, the light globe is 60 Watts.
60 / 240 = 0.25 Amps or 250 milliamps.

Now we can work out the resistance of the light bulb..

240 / 0.25 = 960 Ohms. Without even turning the light off !!

The boring stuff is ….

Voltage x Current = Power
Power / Voltage = Current
Voltage / Current = Resistance
(Current x Current) x Resistance = Power (I^2)xR = P

Even more boring … In formulas you’ll see them as

E=Voltage
I=Current
R=Resistance
P=Power

[Super Max Power]

I love this kind of dirty talk trash. More formulars for everybody. I think I need to expand on my spring compression lecture…

[merc-blue]

ahh a bit of yr11 physics

[trash]

is that year 11 these days ???
I thought simple algerbra was like year 6 ?

[merc-blue]

yeh but yr 11 physics u do ohms law!!

[trash]

I thought year 11 you do calculus !!!
I know which one I find more difficult ! 🙂

The more you try leave the formulas out, the less meaning the descriptions seem to have.

Most year seven students can handle simple algerbra and know how to use a basic calculator.
I’m guessing most of you kiddies are in high school ?

[betty.k]

well i aint exactly a kiddie (31), so i can’t even remember if i learned that or not. but i did now, thanks trash:8ball:

[leonli17]

I learnt it in Year 9. But trash, merc-blue means that Ohms Law was learnt in Year 11 Physics. Not Algebra.

[merc-blue]

algebra is yr 7 …. calculus u learn in yr 11 maths and ohms law u learn in 11 physics..

[Pork_Hunt]

I personally did Ohms law in yr 8 electronics

[trash]

Thanks pork hunt. I was begining to worry that ohms law was going to become a playstation game.
you’ve restored my confidence in the young punks of today. 🙂
Ever since they banned fireworks, I’ve wondered how kids are going to learn high velocity chemistry too. 😯

[leonli17]

As they banned fireworks. Kids start doing illegal stuff more often. Such as, getting fire works illegaly.

[micro_Amps]

Or blowing up letter boxes with recipes found on the internet. (Damn neighbours kids)
Next time I’m calling the bomb squad 😀
:)uA

[jamiekulhanek]

Ahhh fireworks….damn they were fun. Until some dickhead decided to ban them!! Now we gotta find other illegal stuff to have fun with:shock:

[ph2t]

Quote:

Ahhh fireworks….damn they were fun. Until some dickhead decided to ban them!! Now we gotta find other illegal stuff to have fun with:shock:

GUNPOWDER!

ph2t.

[trash]

Sounds like you lived in my neighbourhood uA.
I did some evil sh1t as a kid, hell, I’m still doing evil stuff now.. it’s just a bit less illegal.

I’ve managed to break a few windows, scatter a few bricks in the streets, science labs definately weren’t safe, though most unauthorised experiments were transfered to the garbage bin out front of the principal’s office. Nobody likes the fun police !

I don’t like gunpowder ph2t. It burns too slow !
Think 4500fps or faster !

[betty.k]

this is quickly turning into the ‘old timers remember days of yore’ thread!!:D nothin’ like blowing up a lego car with an insect (or worse!) passenger with your bag of explosives bought at the local milk bar! here’s to the old days!!:8ball:

[ph2t]

Quote:

I don’t like gunpowder ph2t. It burns too slow !
Think 4500fps or faster !

Dude, you gotta get the quick burning stuff. Besides it’s all about presure, steel wool, and a really long cable……..oh yeah and a 9V battery to get the party happening!

ph2t.

[trash]

hahah …. burn is just a simple word for oxidisation and reduction.
When you have long carbon chain molecule and some nitrogen and lots of oxygen and hydrogen.
At 4500fps pressure builds quickly up without a container !

Quote Ralph from the Simpsons: “I like to burn things.”

👿

[Author]

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