# Physic revision

?
• Created by: Courtney
• Created on: 04-02-11 23:29

## Static electricity

-there are two types of electric charge : positive and negative

-the movement of negative electrons from and onto a substance makes it statically charged.

-for example rubbing a rod with a cloth will make the electrons from the cloth jump to the rod, making it statically charged.

1 of 4

## How a photocopy is made

-put the original image in the photocopier

-the copying plate is charged with electricity

-an image of the original is then projected onto the plate

-the charge leaks away where light falls on the plate

-the parts of the pate that are still charged pick up the black powder

-the powder is transferred to a piece of paper and heated so it sticks

-then you have a perfect copy

2 of 4

## Formulas

-resistance= voltage / current

-power= current x potential difference

-current =power / potential difference

-potential difference= power / current

-charge= current x time

-current= charge / time

-time= charge / current

-energy transformed= potential difference x charge

-work= force x distance

-weight= mass x gravity

-kinetic energy= 1/2 x mass x (speed x speed)

-speed= distance/time

-velocity= momentum/mass

-acceleration= change in velocity/time taken

3 of 4

## Electrical components

-diode: an electrical component that only let's electricity through one way
-thermosistor: resistance changes when the temperature changes (on a graph a negative correlation)
-light dependent resistor: the resistance depends on the brightness of the light that falls on it (on a graph a negative correlation)
-motor
-cell
-battery
-bulb
-voltmeter
-ammeter
-field resistor
-variable resistor
-motor
-switch

4 of 4