Electrostatics Flashcards
what is current?
current is the rate of the flow of charge
Equation
Q = It
charge = current x time
what causes current
a flow of electrons
Electric Conductors
Metals, Graphite. allow the flow of electrons
Electric Insulators
plastic, wood. do not allow flow of electrons
how build up electrostatic charge using friction
rub two insulating materials together the electrons will be transferred from one to the other and a charge builds up
when rubbing an insulator on polythene electrons are
transferred from the object to the rod (negative charge in rod)
when rubbing an insulator on perspex electrons are
transferred from the rod to the object (positive charge in rod)
How measure speed of sound in air
stand 400m away from someone with a clapper. Record the time it takes between when you see the clap and hear the clap.
dangers of Electrostatics refuelling planes
fuel is highly flammable. Fuel is a liquid insulator and when passed through pipes at a quick rate, charges are picked up. If there is a spark in the plane, there is a risk of explosion.
uses for Electrostatics
photocopiers and inkjet printers
how photocopiers and inkjet printers work
- An image of the document is projected onto a positively charged copying plate
- The dark parts retain a charge and the light parts lose the positive charge
- black toner powder(photocopier) or ink(inkjet) that is electrically charged sticks is attracted to the positively charged parts of the paper. paper is heated to make powder/ink stick
insulation
placing an insulator over a conductor to prevent electric current from going to another conductor.
double insulation
an extra layer of insulation
earthing
creating an electrical path into the ground in case of electrical malfunction
fuses
melt if the circuit’s current goes too high breaking the circuit. often found near the live wire in mains
circuit breakers
automatic electric switches that protect circuits from overloading/short circuiting
Mains electricity is … current
AC
Batteries are … current
DC
Difference between AC and DC curent
DC current flows only one way and is unchanged in terms of current flow. AC current flows one way and back the other way and is not constant. AC current looks like a wave DC current is a straight line
