How Do Home Appliances Manage Fluctuating Circuit Currents?

[seang]

So I've finished all of my introductory EE courses, that is, the last thing I've learned is complex power.

I was sitting at home one day thinking about how circuits in homes run. I know greedy appliances are put on their own circuit, but a lot of circuits contain more than one appliance. So, if different appliances are on or off, the current in the circuit changes, right? How do appliances handle that?

Also, given my level of education, can anyone suggest some summer reading? Maybe not too far out, but something that could extend or strengthen my education.

 

[Danger]

I can't begin to understand what level of education you're at. The term 'EE' means nothing to me. Appliances don't handle anything other than their assigned job. If their combined amperage exceeds that specified by the breaker, they shut down.

Edit: Hey, does EE stand for Electrical Engineering? If so, you're way ahead of me.

 

[burnhard gandah]

I was sitting at home one day thinking about how circuits in homes run. I know greedy appliances are put on their own circuit, but a lot of circuits contain more than one appliance. So, if different appliances are on or off, the current in the circuit changes, right? How do appliances handle that?

The reason why the appliances draw different currents is because they are connected in parallel. If they were connected in series the same amount of current would pass through them.

 

[berkeman]

So I've finished all of my introductory EE courses, that is, the last thing I've learned is complex power.

I was sitting at home one day thinking about how circuits in homes run. I know greedy appliances are put on their own circuit, but a lot of circuits contain more than one appliance. So, if different appliances are on or off, the current in the circuit changes, right? How do appliances handle that?

The appliances present a complex impedance to the line when turned on, so the current that flows in each is related to the source voltage and the source impedance of the line. If one appliance is drawing a lot of current down a long feed, then that voltage drop will be seen by another appliance in parallel with it and near it. It's common to see lights flicker at motor startup on an appliance like a vacuum cleaner, for example. Motor startup current is typically the max current that will be drawn by an appliance.

Also, given my level of education, can anyone suggest some summer reading? Maybe not too far out, but something that could extend or strengthen my education.

That's a hard question without knowing more about what you consider "done with intro EE classes". Does that mean you've finished your first two years of college? By the end of my first two years of college, I had been through a lot more than complex power (no insult intended, I just am having trouble sync'ing up with what you are saying).

If you would like a very good basic book that will help you round out your knowledge of circuits, I'd recommend "The Art of Electronics" by Horowitz and Hill. If you read that book cover-to-cover and build some opamp circuits and other circuits to play around with, you will have a very good and practical electronics foundation to build upon.

If you really are done with your first two college years in an EE program ("done with lower division"), then I'd suggest a couple of books:

-- "High-Speed Digital Design, A Handbook of Black Magic" by Dr. Howard (Howie) Johnson. This is the most practical and useful high-speed design book you will find, and it has many great tips in it. Howie authors a column for EDN or one of the other big publications (I forget which), and wrote some of this book while he worked here at Echelon where I work.

-- "Designing Digital Filters" by Charles Williams. This is a very fun book for self-study, and covers digital filters (and even some analog filter concepts) in a very intuitive and understandable way. You'll find yourself coding up filters very quickly, even just in Excel to try things out.