## Friday, 12 December 2008

### Charge

Electric charge is a fundamental property of matter which is the cause of all electrical phenomena. Charge is not energy. Charge is acting as the carrier of the energy. Electrical energy is an electromagnetic radiowave which works at extremely low frequencies (electrical systems are generally 50-60 Hz). Charge and energy move differently - in AC cables the charges sit in one spot and wiggle, while the energy flows along at almost the speed of light. What is it that has these charges wiggling in an AC circuit? The charges, it would appear, are repeatedly attracting and repelling one another. Does this suggest two directions of flow at work in the cable?

Electric currents are not just flows of electrons they are flows of electric charge. In order for current to flow, it must be in a closed path called a circuit. To keep the charge flowing there must be a potential difference between two points in the circuit. A conventional current flows from a higher potential to a lower potential as a positively charged particle should. This conventional idea about current flow began with Benjamin Franklin in the 18th Century, before anyone knew what an electron was. When the electron was discovered in 1897, it was found to have a negative charge! Basically, on paper, the current is shown flowing from positive to negative. However, scientific convention would choose the current to be a flow of electrons, and that they are flowing from a higher potential (negative plate) to a lower potential (positive plate).

Before we allow ourselves to become too confused about which is the correct direction of flow, let us examine it from the more recent field of quantum physics. Quantum physics supposes that the flow of negative charge (electron) and positive charge (aka 'hole flow') are approximately equal in probability. A lightning strike can be thought of as a current flowing in both directions; thus making a circuit. This site explains a bit more about it:
http://www.srh.weather.gov/srh/jetstream/lightning/lightning_max.htm

Batteries and generators cause electric charge to flow. Electricity is the flow of charge around a circuit carrying energy from the battery (or power supply) to components such as lamps or motors. Electricity can only flow if there is a complete circuit from the battery through wires to components and back to the battery again. A standard AA battery has a difference of 1.5 volts between its positive and negative terminals. One terminal has a higher potential energy than the other terminal. If we add a piece of wire between the two terminals we create a circuit. We think of the energy moving from the higher potential to the lower potential. Charges from the higher potential are attracted to the lower potential (rather like a boulder at the top of a hill is attracted to the bottom of the hill). But lightning strikes show us that charges from the lower potential are also attracted to the higher potential. Is it not also true for magnets that north and south poles attract, not simply one to the other, but attract each other?

Many thanks to all the sites for all their insights.....
http://en.wikipedia.org/wiki/Magnetic_field
http://amasci.com/viselect/vedemos.html