Solved Ohm's Law

[DreadStarX]

So, I'm sitting here in my Cisco Class, struggling to understand these questions, and what not.

This is, by far, the most trouble I have ever had, relating to computers.

Here is one of the questions.

5. The yellow wire connected to a power supply carries 12V. If the power supply provides 60W of power to the yellow wire, how much current is passing through the yellow wire?

I came up with 5 Amperes aka 5 Amps. But I'm not entirely sure.

Anyone got some nifty tricks to help me learn this?

 

[Britton30]

 

[AmericanPharaoh]

I feel like I'm helping you cheat on a test. Divide 60 by 12 = 5.

 

[DreadStarX]

I feel like I'm helping you cheat on a test. Divide 60 by 12 = 5.

Nope. I was given similar materials as to what was posted above, except it confused the hell out of me.

So it's I = P / V which translates to Current equals (=) Power / Voltage / I = 60W / 12V. I = 5 Amps


I came up with the answer, but again I was confused. This should tell you why.

 

[derekimo]

Your answer is right, what part confuses you?

Here's a calculator to check your math.

Ohm's Law Calculator

60W/12V = 5A

 

[DreadStarX]

Your answer is right, what part confuses you?

Here's a calculator to check your math.

Ohm's Law Calculator

60W/12V = 5A

Well.. Having so many options opposed to having just 3. Like this question I have here.

3. Re-arrange the Ohm's Law equation to solve the following:

R =

And thats it. But now that I've looked at it; its literally the same equation for what you previously answered, only backwards. R = W / V. Least I think its that.

 

[derekimo]

R = W / V. Least I think its that.

Not quite, it's any of these 3 below depending on what you already know.

If you want to use Watts and Volts it is R = V²/ W

 

[DreadStarX]

Well... If Ohm's Law is V = I*R then, wouldn't R = V / I be it then? Because V = I*R is the original equation.


As you can see, my mathematical intelligence is fairly low when it comes to things of this caliber. But I still try

 

[derekimo]

Well... If Ohm's Law is V = I*R then, wouldn't R = V / I be it then? Because V = I*R is the original equation.

Yes it would.

I just gave you the correct way with the previous terms you used, which was with Watts and Volts.

 

[Britton30]

Ohm's law would be easier if it used
W=watts
V=volts
A=amps
O=resistance
The "I" and "P" and always confuse me.

 

[derekimo]

Ohm's law would be easier if it used
W=watts
V=volts
A=amps
O=resistance
The "I" and "P" and always confuse me.

And just to add to the confusion is the PIE chart,

 

[Britton30]

Gee, thanks Derek.

 

[derekimo]

Gee, thanks Derek.

Thankfully, that's not in common use anymore.

Does make for a confusing chart,

P = W

I = A

E = V

 

[A Guy]

Years ago, Native American Indians used to roam the plains of the United States. These Indians would look across the plains, and see all kinds of animals. They would see rabbits running across the field, and eagles soaring in the sky. Now, picture things from the Indian's stand point - he sees the Eagle flying over the Rabbit:

Say to yourself Indian equals Eagle over Rabbit.

Now just use the first letter of each word: I = E over R

However, from the Rabbit's point of view, he sees things a little differently. The Rabbit looks out and sees the Eagle flying over the Indian.

Say to yourself Rabbit equals Eagle over Indian.

Now just use the first letter of each word: R = E over I

Finally, the Eagle up in the sky sees both the Indian and the Rabbit standing on the ground together.

Say to yourself Eagle equals Indian and Rabbit together.

Now just use the first letter of each word: E = IR



A Guy

 

[derekimo]

That's a good one Bill.

 

[Britton30]

Very good association Bill, deserves a rep.

 

[Northernsoul55]

You don't need all those charts really , you just need to be able to
transpose the formula using basic algebra:

Example:

Transpose the formula V = I x R, to make I the subject.


V=I x R (Divide both sides by R)


V=I x R
_ ___
R R

The R's on the right cancel each other out.

So you get:

V=I
_
R

Then flip the formula round to read:

I=V
_
R

To get to I just simply "times" both sides by R

R x I= V x R
_
R

The R's cancel each other out and you get to:

I = V X R

It is same method if you want to make V the subject.

 

[Britton30]

What's algebra?

 

[Bongo]

 

[A Guy]

A Guy