# Homework Help: Electrical Outlets at home

1. Apr 25, 2012

### doublemint

My friend asked me why do houses have electrical sockets that output a constant voltage rather than a constant current.
For the life of me, I couldn't answer it..

Anyone help me out?

Thanks,
DM

2. Apr 25, 2012

### Staff: Mentor

The current drawn from the voltage source is dependent on the resistance of the load, according to Ohm's Law:

[STRIKE]V = V x R[/STRIKE] V = I x R

Or

I = V/R

Constant current sources have their applications in electronics, but not in power distribution. You use voltage sources for power distribution.

EDIT -- Just to add a bit more... Common power sources like batteries and electric generators are voltage sources, not current sources.

Last edited: Apr 25, 2012
3. Apr 25, 2012

### rollcast

I forget now how it works (I'm sure some one can correct me) if you where to use constant current then the frequency would vary with load which would mean certain devices such as synchro motors wouldn't spin at a predictable speed.

4. Apr 25, 2012

### Staff: Mentor

If you used an AC current source, why would varying the frequency change the power output (to adjust to the load)? I'm not understanding what you are saying...

5. Apr 25, 2012

### rollcast

I asked my physics teacher this same question one time and he said that if you had a constant current ac source then the frequency wouldn't be constant and that would affect ac powered motors?

6. Apr 25, 2012

### Staff: Mentor

I'm sure you mean V = I x R.

7. Apr 25, 2012

### Staff: Mentor

Oops, thanks for catching my typo, Mark. I'll strikeout and fix my post above. Thanks.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook