Which Types Of Materials Can Be Charged?
All insulating materials (not metal) can be charged
You Charge Them By... Rubbing actions with another insulating not material
So... Polythene rod (neg) rubbed against a dry cloth (positive)
To Charge an object with a negative charge it must gain electons.
It charge an object with a positive charge it must lose electons.
Static Electricity P2 4.1
Static electricity can build up when 2 insulating materials are rubbed together. The FRICTION moves ELECTRONS from one material onto another. One will beome + and one will become -.
+ + + = Repel - + - = REPEL + + - = ATTRACT
SO.... A polythene rob become negatively charged when rubbed with a duster because it GAINS electrons.
If a negativly charged object is connected to earth by a metal strap from the object to the ground the object will become safely discharged.
USES... Photocopier and smoke precipitiors
Van de Graaff P2 4.1
The van de graaff becomes charged as the belt (insulating material) rubs against the polythene reel. Then th belt gains electrons to friction. When the negativly charged belt comes in contact with thepositivly charged metal ba they attraced.
It charges up because: The belt rubs againsst a felt pad and beocmes charged. The belt carries the charge onto an insulated metal dome. Sparks are produces when the dome can ni longer hold anymore charge,
Electrical Circuits P2 4.2
CURRENT? The number of electrons that passes a point per second.
POTENTIAL DIFFERENCE? (voltage) The energy per unit charge
RESISTANCE? The potential difference reqired to drive one amp through a component
i = Current / amps/ a W = energy transfered/ J
Q = charge / cowloons / C Q - charge/ C
T = time/ seconds/ s Q W
V = Potential difference/ V V I T V Q
R = resistance R I
A characteristic curve is a graph showing current on the y axis and the potential difference on the X axis for an electrical component
RESISTOR... Always straight line through origin/ The current and P.D are directly proportional to each other
BULB... gradient becomes ahallower as current increases/ goes through origin
DIODE... acts like a one way gate for current. It will only flow in a positve direction.