### Author Topic: Ohm's Law  (Read 5135 times)

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#### rockrobotics

• Jr. Member
• Posts: 46
##### Re: Ohm's Law
« Reply #30 on: March 11, 2010, 07:54:02 PM »
That's what I tried to tell them! (But not in the same words) LOL
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#### cyberfish

• Robot Overlord
• Posts: 163
##### Re: Ohm's Law
« Reply #31 on: March 11, 2010, 10:46:02 PM »
Is there any rule that says the symbolic name cannot be the same as the unit? Or that the symbol for a quantity cannot be the same as the symbol for its SI unit?

I am finishing my second year EE in Canada (British Columbia), and I have never seen/heard the use of U for voltage. My professors are from all over the world (mostly North America, though), and none of them use U.

Just because we use the same symbol for the quantity and the unit doesn't mean we don't know better and are "wrong".

#### Daanii

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• Posts: 138
##### Re: Ohm's Law
« Reply #32 on: March 12, 2010, 01:34:53 AM »
Others seem to have tired of this discussion, but I still find it interesting.

"Is there any rule that says the symbolic name cannot be the same as the unit?"

The point is, the name and the units are different. Electromotive force is measured in volts. Current in amperes. Resistance in ohms. It violates the rules of logic and consistency to use volts, current and resistance in an equation.

For example, in mathematics there is a convention to use x, y and z for variables and a, b and c for constants. If I write an equation a = x + c, and I intend for the a to be a variable, I'll probably confuse people. Better to write y = x + c.

Same for V = IR. As Soren points out, that may confuse people. It's like babbling. Better to stick to conventions than to risk misunderstandings.

But with V = IR, the reverse may now be true. Few people use the term electromotive force anymore, so using E may be confusing. Just like no one calls "current" by its original name of "intensity."

It's an interesting issue. I don't think there is a wrong or a right. I can see grounds for both E = IR and V = IR.
« Last Edit: March 12, 2010, 01:37:15 AM by Daanii »

#### cyberfish

• Robot Overlord
• Posts: 163
##### Re: Ohm's Law
« Reply #33 on: March 12, 2010, 02:23:07 AM »
Well, in my part of the world, convention (what people are used to) seems to be V=IR.

Using E would be very confusing, since we use that for electric field strength (gradient of voltage).

#### nottoooily

• Full Member
• Posts: 91
##### Re: Ohm's Law
« Reply #34 on: March 12, 2010, 05:57:33 AM »
There's also the convention that the variable name is the first letter of the name of the quantity:
R - resistance
I - intensity(?)
m - mass
v - velocity
F - force

So to be consistent we better use
V or v for voltage or
E for electromotive force but
U for Maybe that's the inconsistent oddball that should be avoided.

#### richiereynolds

• Full Member
• Posts: 112
##### Re: Ohm's Law
« Reply #35 on: March 12, 2010, 08:26:54 AM »
It's not even a real law here, I never pay any attention to it and I've never been arrested.

• Contest Winner
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##### Re: Ohm's Law
« Reply #36 on: March 12, 2010, 12:35:24 PM »
It's not even a real law here, I never pay any attention to it and I've never been arrested.

HAHAHA you almost made me spit out the drink i was enjoying as i read this.

#### rockrobotics

• Jr. Member
• Posts: 46
##### Re: Ohm's Law
« Reply #37 on: March 12, 2010, 04:03:13 PM »
Yay!

Now I'm like a web sensation for posting
a simple question!
Rock Robotics

Technology of the Future!

#### Soeren

• Supreme Robot
• Posts: 4,672
##### Re: Ohm's Law
« Reply #38 on: March 12, 2010, 08:51:01 PM »
Hi,

Now I'm like a web sensation for posting
a simple question!
Hate to burst your bubble, but you'll quickly learn that posting (here or anyplace else on the net) something simple, like what resistor for an LED, is the sure way to get everyone and his dog answering.

The number of people answering a post is usually inverse proportional with the degree of difficulty, which is somewhat logical, since fewer people will be able to answer the hard ones (correctly at least, as some people will post whether they know the answer or not).
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Engineering is based on numbers - not adjectives

#### rockrobotics

• Jr. Member
• Posts: 46
##### Re: Ohm's Law
« Reply #39 on: March 13, 2010, 09:55:04 AM »
Okay,

I was just kidding, you know that right?
Rock Robotics

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#### Daanii

• Robot Overlord
• Posts: 138
##### Re: Ohm's Law
« Reply #40 on: March 13, 2010, 12:36:24 PM »
This is a serious forum. Dedicated to the discussion of robots. We don't joke or kid here.

#### rockrobotics

• Jr. Member
• Posts: 46
##### Re: Ohm's Law
« Reply #41 on: March 13, 2010, 12:39:56 PM »
Woooooooooooow,

You don't have to get all stressed for nothing!
Rock Robotics

Technology of the Future!

#### Daanii

• Robot Overlord
• Posts: 138
##### Re: Ohm's Law
« Reply #42 on: March 13, 2010, 12:46:51 PM »
I'm kidding.

#### GWER57

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• Posts: 65
##### Re: Ohm's Law
« Reply #43 on: March 13, 2010, 12:53:26 PM »
Servos are cheaper because they do not use as good motors / gears as other dc gear motors. BUT, servos are still awesome, they are easy to control, mount and connect to wheels and are probobly better for small robots.
GTW

• Jr. Member
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