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### Author Topic: Ohm's Law for Idiots  (Read 3754 times)

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#### _Moonbot_

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##### Ohm's Law for Idiots
« on: February 16, 2011, 10:31:26 AM »
I'm new to robotics and was wondering if someone could explain Ohm's Law to me.
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#### blackbeard

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##### Re: Ohm's Law for Idiots
« Reply #1 on: February 16, 2011, 10:53:14 AM »
ohms law basicly shows the relation between resistance, current and voltage. look at the wheel below

instead of E you can use V for voltage. by shifting arround a the ohms law calculation you can find current, voltage and resistance using any of the other 2 variables. If for instance you have a 1.5v battery with an unknown resistor.

you measure 0.00075 amps. with that info you could find out what the resistor is through the ohms law calculation R=E/I or R=1.5/0.00075. the answer is 2000 meaning you have a 2k resistor!
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#### newInRobotics

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##### Re: Ohm's Law for Idiots
« Reply #2 on: February 16, 2011, 11:09:35 AM »

Once I've read a nice explanation of Current, Voltage and Resistance is. It goes something along these lines.

If You compare electricity to Your house water system:
Voltage is a Water Pipe
Current is a Water Flow
Resistance is a Valve(or a tap)

Now, You can imagine that the bigger the Water Pipe the bigger Water Flow is.
Same with electricity, the bigger the Voltage, the more Current You can get.

If You have a Valve(or a tap) You can reduce Water Flow with it because size of the Water Pipe is reduced at that spot (if You get what I mean), hence with Resistance (Resistor) you can reduce Current by creating a Voltage drop at a certain spot in a circuit.

That's what Ohm's Law is about.

I - Current
V - Voltage
R - Resistance

I = V / R

V = I * R

R = V / I

There is a nice free simulation software called Yenka that has loads of useful and interactive examples on basic electronics.

Take care
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#### TrickyNekro

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##### Re: Ohm's Law for Idiots
« Reply #3 on: February 16, 2011, 12:47:11 PM »
If You have a Valve(or a tap) You can reduce Water Flow with it because size of the Water Pipe is reduced at that spot (if You get what I mean), hence with Resistance (Resistor) you can reduce Current by creating a Voltage drop at a certain spot in a circuit.

That's not entirely accurate... The voltage drop is the consequence not the form factor... Resistance is the form factor... Or even better applied voltage at a closed circuit is the form factor...
Ohm's law says that the current is analogue to voltage applied in a close circuit of certain resistance... ;-)

That's more obvious if you know about non lineal components like diodes where there is always a voltage drop added to ohmic voltage drop...

Anyways, I'm just saying! That color example was a very nice writing!!! Keep it up mate ;-)
For whom the interrupts toll...

P.S. I've been inactive for almost a year... Don't give promises but I'll try to complete my tutorials. I'll let you know when..

Cheers!

#### newInRobotics

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##### Re: Ohm's Law for Idiots
« Reply #4 on: February 16, 2011, 01:03:24 PM »
That's not entirely accurate... The voltage drop is the consequence not the form factor... Resistance is the form factor... Or even better applied voltage at a closed circuit is the form factor...
Yes , You are correct, voltage drop is a consequence of by resistance reduced current; I've expressed myself that way to make it easier to understand the basic concept.

Take care
"Computer games don't affect kids; I mean if Pac-Man affected us as kids, we'd all be running around in darkened rooms, munching magic pills and listening to repetitive electronic music." - Kristian W

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