Make Ex 5 Notes

That's pretty good.

I think there are a few improvements we can make...

I'll go along with that.

This one is a bit tricky. You'll have to explain where you got this from. As it stands, it needs improvement, I'm just not sure what way it needs to go.

That seems OK

The first part of this is a bit messy (where do you get this from) but the second is essentially correct. When there is no more material left to react, the reaction cannot continue and the battery is indeed flat.

Hmmm... primary batteries are manufactured in a charged state and normally cannot be recharged. It is designed to be used once (or until flat) and then discarded

it's not always raw metal, although it may well be.

Not completely sure what you mean here. If you mean that the electrons which are forced out of a battery are sent along wires to power electronic devices, then yes, but it's not so much the electrons themselves as it is the force which pushes them that we're interested in.

They do! (outside of the battery)

yep

it's actually a unit of charge, essentially the equivalent of a number of electrons

yep

it is also 1 watt expended for a period of a second (Watts are Joules per second.)

generally speaking they change one substance into another in a way that releases energy. A metal to a metal oxide is one of these -- essentially you're burning metal, and burning releases energy.

often, but not always. Turning a metal oxide back to a metal requires the addition of energy. Inside a battery you may not be able to do this. The ability to do this is generally a marker of what makes a cell primary or secondary.

they do

that too!

not really. in your examples above, the batteries would go flat after the same amount of energy was taken out. Energy is power time time. if we want to do it in the same time we need to keep the power the same. And since power is voltage times current, we need to draw half the current when the batteries are in series as we do when the two of them are in parallel. In this case, you can draw a higher current for longer from the LOWER voltage collection of batteries. This is (one reason) why you place batteries in parallel, to allow you do draw more current.

Maybe we can get you some slightly better wording. See what others have to say.

 

You are, of course, exactly right. I'll edit for my brain fart

Hang on, I said "Watts are Joules per second". "Joules are Watt seconds" is an equivalent statement.

J = W.s

=> J/s = W.s/s .... (for s <> 0)
=> J/s = W

 

I'm not sure what you mean. A Watt *IS* a Joule per second.

See here:

Anyway, I'm sinister, not sophist.

 

no, not an accurate definition, as that would include rechargables
In addition to what steve said -- the other standard meaning for primary is in the term

Primary Cell like your 1.5V cell size AAA, AA, C, D or those big 1.5 volt ones used in the old telephone systems etc

they are not BATTERIES a Battery is a collection of CELLS
its just that everyone has got use to calling AAA, AA etc cells batteries but technically its incorrect

your small 9V batteries ARE batteries if you open a dead one up, you will find its made of of a number of cells. A car battery is also a real battery as it is also a collection of cells

no not really, infact probably very rarely. The battery/cell dies - goes flat when the chemical reaction can no longer be sustained. Take a AA cell, it has only 1 metal electrode ... the zinc casing ... when the battery is flat, that zinc casing is still very intact
definately NOT used up
the other electrode is a carbon rod, it is centred down the middle of the cell and the area between it and the zinc case electrode is filled with a chemical compound

cheers
Dave