Newbie needs help with basics

So to summarize what I have learned:

1) Find total resistance in curcuit 1a) use formula R=E^2/P if R is unknown but P & E are known 2) Find (total) current in circuit by using RT and VT 3) Find voltage drop of each load and ensure it's adequate for each load

Excellent ! I learned a lot from this post !!

One small question...why do we square the voltage in the formula R=E^2/P ? Why can't we just use the actual voltage ?

TIA

Think of these two equations:

P = E*I and I = E/R

Let's assume you believe those.

Combine them and you get

P = E * E/R or E^2 / R

So we have to use E^2, not just E.

Mark

Ahh ! we're breaking out the I into it's component parts. I see. great, thank you !

I agree that 3.6 ohms should have been a choice or things should have worked out so that 5 ohms was an exact answer. As an adjunct electronics instructor I can tell you that these kind of poorly thought out problems are the best way to confuse students. You need to build up the students confidence using ohms law formulas before you present them with problems like this one. The point may have been to get students to think in generalities but they are more confusing than helpful.

Dorian

--- If you'd be so kind as to leave a little of the post you're replying to in your reply, then we all could see to whom and to what you're responding.

Guidelines from:

"Summarize what you're following up.

When you click "Reply" under "show options" to follow up an existing article, Google Groups includes the full article in quotes, with the cursor at the top of the article. Tempting though it is to just start typing your message, please STOP and do two things first. Look at the quoted text and remove parts that are irrelevant. Then, go to the BOTTOM of the article and start typing there. Doing this makes it much easier for your readers to get through your post. They'll have a reminder of the relevant text before your comment, but won't have to re-read the entire article. And if your reply appears on a site before the original article does, they'll get the gist of what you're talking about."

-- John Fields Professional Circuit Designer

You have to look closely at the bulb. :-( They show it burned out. Ed

--- LOL, yup, you're right!

I also missed the bit on the bottom of the page where the bulb makes reference to being burned out.

Thanks,

-- John Fields Professional Circuit Designer

to in your reply, then we all could see to whom and to what you're responding.

will do !

j