{{:electricity:electricity-banner-790x50.jpg|Electricity Banner}}
====== Q7.1 What is the difference between battery types: ======

=== CORE CONCEPTS: ===
Understanding how batteries work & various battery characteristics. 

What is the difference between the types: 'D'. 'C', 'AA'  and 'AAA' battery cells 

++++ Q7.1 CLICK HERE TO SEE / HIDE STUDENT FLIP RESOURCES:|
{{youtube>cxkVxi9P0EA?640x360|Battery Capacity}}
**Video: Battery Capacity**
  * IF UNABLE TO ACCESS YOUTUBE VIDEO (requires Flash) TRY:[[http://viewpure.com/cxkVxi9P0EA|Battery Capacity]]

**An Example Flashlight Battery Cell Comparison Chart**
  * [[http://www.epectec.com/batteries/cell/|Flashlight Battery Chart]] - Compare the values 'Nominal Voltage' and the 'Typical Capacity' columns - bigger numbers are better. In most cases, the larger the battery, only the Capacity is larger - not the voltage. This means the battery provides power for a longer period but doe not make lights burn any brighter or motors more powerful than smaller batteries having the same voltage value.

++++

++++ Q7.1 CLICK HERE FOR A SCIENTIFIC EXPLANATION:|
All other things being equal, bigger batteries can run lamps for a longer time

MISCONCEPTION: 'Batteries Store Electricity'

The idea that batteries store electricity is NOT RIGHT!

Electric currents in copper wires are a flow of electrons, but these electrons are not supplied by batteries. Instead the electrons come from the wire.

In copper wire, copper atoms supply the flowing electrons. The electrons in a circuit were already there before the battery was connected. They were even there before the copper was mined and made into wires!

Batteries and generators do not create these electrons, they merely pump them, and the electrons act like a pre-existing fluid which is always found within all wires.

In order to understand electric circuits, we must imagine that all the wires are pre-filled with a sort of 'liquid electricity'.

Wires are not like hollow pipes. They're like pre-filled pipes... with no bubbles allowed.

To complete the picture, add this:

**All conductors are always full of movable charge. That's what a conductor is, it's a material which contains movable charge.**

----
++++

====== Q7.3 Why are at least two wires needed to make a circuit: =======
This may seem like 'trick' question but, hopefully a deeper understanding reveals that it is not 'a trick':

Only ONE wire is required:

Some obvious examples of single wire circuits include items such as:
  * Electromagnetic Coils/Chokes
  * Transformers
  * Some low voltage gloves and similar ski/winter clothing
  * Simple electric space-heaters
  * Induction loops
  * Fuses

Less obviously, all circuits only really require one wire if you think of them as a simple loop.

++++ Q7.3 CLICK HERE TO SEE / HIDE STUDENT FLIP RESOURCES:|
{{youtube>fDfrdcs65HY?640x360|Resistance & Single Wire Circuits}}
**Video: Resistance & Single Wire Circuits**
  * IF UNABLE TO ACCESS YOUTUBE VIDEO (requires Flash) TRY:[[http://viewpure.com/fDfrdcs65HY|Resistance & Single Wire Circuits]]

A single wire, a resistor, or anything that connects positive + negative terminal (including a 'short')

----
++++

++++ Q7.3 CLICK HERE FOR A SCIENTIFIC EXPLANATION:|
When current is flowing in a wire circuit, it accelerates when there is no resistance in the circuit. The unrestrained acceleration often leads to over-heating and is therefore dangerous and to be avoided.

=== WHY ARE TWO WIRES NEEDED? ===
This question can be mostly understood by considering an analgous question:

When you need to set up a pulley and belt system that rotates in a loop, are two belts needed?

The answer: Two belts are not required: There is only one belt, and the belt forms a circular loop. It looks like there are two belts, with one of them flowing leftwards and the other one flowing right. But in truth, there is just one belt, and it is rotating. 

So, why are two wires needed?

The answer: There are not two wires!

Instead there is only one wire, but it is connected in a circle. All metals are full of movable electrons, so when we connect a wire in a circle, we are forming a kind of "electric drive-belt" which can move inside the wire. 

But household electric outlets have three prongs!

Yes, but only two of them are used. The third one is only used for safety purposes.

----

++++