1.4.1 Electrostatics
Objects are normally uncharged, and insulators can gain charge through friction. A charged object can attract uncharged objects. A negatively charged object will repel another negatively charged one, and a positively charged will repel another positively charged one. Negative charge was the name given to the type of charge on an amber rod when rubbed with fur, and positive charge was the name given to type of charge on a glass rod when rubbed with silk, soon however, other conductors and insulators were found and so these terms were accepted generally. Polythene strips gain negative charge from friction and acetate strips gain positive charge from friction.
1.4.2 Current
Current is de ned as the rate of ow of charge, with equations:
1.4.3 Derivation of Drift Velocity
The equation of drift velocity is derived from four things, the volume of the wire, the total number of electrons per metre3 (a constant for each material), the charge of an electron (a constant) and the equation for current, it is formed as follows:
V = AL
N = nAL
Q = nALe
