P5

Front 1

What causes static electricity?

Back 1

-when two insulating materials are rubbed together, electrons are scrapped off one and dumped on the other.

-this leaves a positive static charge on the material the electrons are scrapped off, and a negative charge on the one getting the electrons

-they try to repel but cant move because their positions are fixed which causes static electricity

Front 2

What happens when the electrons are moved?

Back 2

-particles are left positively charged (ions)

-the protons never move and are only caused by electrons leaving the material

Front 3

What are some examples of static electricity?

Back 3

-attracting dust-particles are attracted to anything that is charged

-clothes-electrons are scrapped off when pulled over your head and they cling to you

-bad hair dyes-hair repels one another

Front 4

What is electric current?

Back 4

-flow of charge

-metal conductors (components, wires) are full of charges (electrons) that are free to move

-the battery pushes the free charges through the wires and flows round the circuit back to the battery

Front 5

What is the difference between current, voltage, resistance and power?

Back 5

CURRENT-will only flow through a component if there is a voltage across it (A)

VOLTAGE-pushes the current around (V)

RESISTANCE-caused by things in the circuit (such as lamps) that slow the charge down.

POWER-is the rate at which an electrical power supply transfers energy through a component (high power=transfers a lot of energy in a short time so uses a large current)

Front 6

What is a voltmeter for?

Back 6

-to measure potential difference between two points (voltage)

-when energy is transferred, work is done so PD is also the measure of work done on or by a charge between the two points

-must be placed in parallel

Front 7

What do voltage- current graphs show?

Back 7

-how the current in a circuit varies as you change the voltage

-the current through a component is proportional to the voltage across it when the resistance stays constant

-the steeper the slope, the lower the resistance

Front 8

How do resistors work?

Back 8

-when electrons move through a resistor, they collide with positive ions in the resistor.

-this makes the ions vibrate more which causes an increase in temperature

Front 9

What are the different types of resistors?

Back 9

-FILAMENT LAMP-contains a piece of wire with really high resistance so when current passes through, its temperature increases and it glows

-LIGHT-DEPENDANT-changes the resistance depending on how much light there is (highest in darkness)

-THERMISTOR-depends on temperature (highest in low temp)

Front 10

What are the rules of a series circuit?

Back 10

-the total voltage of the battery is shared between the components

-the current is the same every where

-the total resistance is the sum of the individual resistances (battery has to push charge through all of them)

-two cells means a bigger voltage but the current doesn't change

Front 11

What are the rules of parallel circuits?

Back 11

-each component is separately connected to the battery.
-if you remove or disconnect one of them, it will hardly affect the others.
-the total voltage is equal everywhere/
-the total current is shared between the branches
-the total resistance is less than the branch with the smallest resistance

Front 12

What is mains supply?

Back 12

-230 V
-produced by generators by electromagnetic induction
-AC (constantly changing direction)
-easier to generate and simpler to distribute over long distances

Front 13

What is electromagnetic induction?

Back 13

-moving a magnet in or near a coil of wire to create voltage and maybe a current
-as you move the magnet, the magnetic field though the coil changes which induces a voltage across the wire.
-if the ends of wire are connected then a current will flow in the wire
-the direction of the voltage depends on the way the magnet is moved

Front 14

How do AC generators work?

Back 14

-a magnet rotates in a coil of wire.
-as the magnet turns, the magnetic field changes which induces a voltage as well.
-when the magnet is turned half a turn the direction of the field reverses which makes the current in the opposite direction

Front 15

What factors affect the size of the induced voltage?

Back 15

-add a iron core inside the coil
-increase the strength of the magnetic field
-increase the speed of rotation
-increase the number of turns on the coil

Front 16

How do transformers work?

Back 16

-transformers are used to change the size of the voltage
-they use electromagnetic induction to step up or down the voltage.
-you have two coils of wire around a iron core.
-the alternating current in the primary coil causes a change of magnetic field and induces a changing voltage in the secondary coil

Front 17

What is the difference between a step up and step down transformer?

Back 17

-STEP UP-increases voltage so has more turns in the secondary coil than the primary coil
-STEP DOWN-decreases voltage so has more turns in the primary coil than the secondary coil

Front 18

What is a magnetic field?

Back 18

-a region where magnetic materials (iron and steel) and wires carrying currents experience a force acting on them
-When the wire is at right angles to the field the force acts at right angles to both the force of the field and the direction of the current.

Front 19

What is the simple motor effect?

Back 19

-If a rectangular coil of wire is placed in a uniform magnetic field (has the same strength everywhere in the field), the force causes it to turn.
-The simple motor effect uses a split-ring commutator to keep the coil rotating continuously instead of swapping every half turn.