239Views22Replies

# I need help in understanding faradays law?

So this is where i was trying to understand his law, http://www.6pie.com/faradayslaw.php, the part that i got stuck was on where it says, "Lets figure 5 turns per second, that gives us 300 RPM. If we do a good blade design we might be able to get 300 RPM in 3 to 5 mile winds.

5 turns per second gives us one turn every .2 seconds

seconds = .2"

I am trying to apply this to a bike and want to know how to get past this step to getting Δt of the formula.

5 turns per second = 1/5 seconds per turn ....0.2 seconds per turn.

Select as Best AnswerUndo Best Answer

ok that makes me understand how you get 0.2 but how does that relate to 300 rpm?

Select as Best AnswerUndo Best Answer

What do you mean "relate to" ?

Something spinning at 300 RPM is spinning once every 0.2 seconds. Or 5 revolutions per second, or 60*5 revolutions (300 RPM) or 60/0.2 = 300 RPM.

Steve

Select as Best AnswerUndo Best Answer

I didn't look at your link but the part that you quoted seems just like simple math to me...

5 turns per second. 60 seconds per minute. 5 X 60 = 300.... or 300 RPM (Revolutions per minute).

Select as Best AnswerUndo Best Answer

You perhaps told me the rpm but i dont think thats how you get rpm due to this tutorial I've found(http://www.ehow.com/how_6088311_calculate-rpm.html) however i need to know how to get Δt of the formula in which the Δt of the example equals 0.2 (Δt=0.2).

Select as Best AnswerUndo Best Answer

This is probably the simplest answer I could find for you...

Faraday's Law: V = -NΔφ/Δt . Here N is the number of loops, Δφ is the change in flux, and Δt is the time required for the change.

So the "time required" for one full turn in the example is 0.2

(5 turns per second gives us one turn every .2 seconds)

How you determine what your number is depends on the RPM you have.

Select as Best AnswerUndo Best Answer

so if rpm is known, how is the formula represented Δt= ?/rpm or Δt=rpm * ?

Select as Best AnswerUndo Best Answer

Δt= 60/rpm

Select as Best AnswerUndo Best Answer

both of them still work but thanks you two :).

Select as Best AnswerUndo Best Answer

No problem. Just don't forget to click one of the blue button's (Steve's). It will mark your question as "answered" and then people like us will stop posting comments. lol :-)

Select as Best AnswerUndo Best Answer

Okie doke :) wish i was able to mark you both but if you insist:)

Select as Best AnswerUndo Best Answer

Doh! That looks much better than my sad attempt at an equation at 2am... o_0

Select as Best AnswerUndo Best Answer

I just cut and pasted.....

GoodNIGHT.

Steve

Select as Best AnswerUndo Best Answer

I wish I could....

_{Sciatic nerve pain... can't lay down to go to sleep. Got the laptop with me on the couch with an ice pack. }Select as Best AnswerUndo Best Answer

OW. Sorry to hear that.

Steve

Select as Best AnswerUndo Best Answer

Thanks.

_{BTW... I sent a reply. I think the filters got it... *sigh*}Select as Best AnswerUndo Best Answer

Got it.

Select as Best AnswerUndo Best Answer

In the example, they've explained that...

They figured out they could get 300 RPM (revolutions per minute)

300 divided by 60 seconds in a minute = 5 full revolutions per second.

But you want the time it takes for ONE full revolution (not 5).

So 1/5 of a second = 0.2 seconds. (The time it takes to complete ONE full revolution).

As an equation, I think you need something like this:

Δt = 1/ (RPM/60)Δt = 1(second) divided by the RPM divided by 60

Select as Best AnswerUndo Best Answer

Δt = 1/ (RPM/60)

= Δt = 60/RPM, by definition.

Select as Best AnswerUndo Best Answer

thank you thats what i was looking for and seems about right

Select as Best AnswerUndo Best Answer

I'd go with Steve's equation.... (and give him the best answer credit). ;-)

Select as Best AnswerUndo Best Answer

You're welcome.

Don't forget to click one the blue buttons so that it marks your question as "answered" on the main page. :-)

Select as Best AnswerUndo Best Answer