Electricity and radiation ( fission , medical , background)

Switch open symbol

Switch closed

Cell

Battery

Diode

Resistor

Variable resistor

LED

Lamp

Fuse

Voltmeter

Ammeter

Thermistor

LDR

Current

How quickly the electrons are moving around the circuit , measured in amperes or amps A

Charge

Electrons carry charge around the circuit , measured in coulombs (C)

Potential difference

The amount of energy carried by each electron, measured in volts

In the UK the current changes direction at a frequency of

50 Hz

Mains electricity has a average potential difference of

230V

Direct potential difference

Direct p.d only points in one direction around a circuit

( given by cells and batteries)

Alternating potential difference

Changes direction , so it points one way , then the other, and back again

( used in national grid )

National grid

The national grid is a system of cables and transformers linking power stations to consumers.

Mains electricity

The electricity supplied to our homes

( alternating )

Transformers - step up

Increases the p.d which reduces the current . Less current —> less energy wasted as heat

Transformers - step down

Reduces the p.d and increases current to a safe level before the electricity is given to consumers

Transformers

Used to increase the efficiency of the National grid

Explain the difference direct and alternating potential difference

Polarity of potential difference doesn't change when direct

Wires in a plugs

Neutral , Earth , live

Live wire

Brown , carries the alternating p.d from the supply , 230 V

Neutral wire

Blue , completes the circuit , close to 0 V

Earth wire

Green and yellow stripes , safety wire to stop the appliance becoming live , 0 V

Electrical Power

Every appliance will tell you how much energy it will use in total every second ( power of appliance measured in Watts )

b

Fuse in a plug

Limit the current that can pass through the circuit ( breaks the circuit if current goes too high )

The pins of a three -pin plug are made of

Brass

A cable consists of a

Copper wire surrounded by insulating material as rubber

Nuclear fission

A nuclear reaction in which a large and unstable nucleus ( e.g uranium)

Nuclear fission steps

- a neutron is fired at the uranium -235

- the neutron is absorbed, the uranium nuclei becomes unstable

- the unstable nucleus splits into 2 smaller daughter nuclei and releases 2 or 3 neutrons, aswell as gamma rays and energy

Chain reaction (nuclear)

a self-sustaining fission process caused by the production or neutrons that proceed to split other nuclei

Chain reaction is controlled by

Control rods which absorb extra neutrons are

Nuclear fusion

Nuclear fusion, if the joining of two light nuclei to form a heavier nucleus in this process of the mass may be converted into the energy of radiation

Transformer equation

potential difference across primary coil x current in primary coil= potential difference across secondary coil x current in secondary coil

( power = power )

background radiation

nuclear radiation that occurs naturally in the environment

Background radiation is around us

all the time

Background radiation can come from

Natural sources ( rocks , sources, cosmic rays from space )

Man-made ( fallout from nuclear weapons testing and nuclear accidents)

nuclear radiation in medicine

exploration of internal organs and the control or destruction of unwanted tissue

Sterilise medical equipment

High doses of gamma radiation can kill harmful organisms/ bacteria. E.g needles can be sterilised as the gamma can penetrate the packaging to kill the bacteria. Especially good on plastic equipment as it could melt.

Medical tracers

Gamma emitters that have suitably short half-lives to be ingested into the body, and be detected externally for the duration of a medical process.

Gamma is used as it is least ionising

Kidney test

gamma camera

A camera that detects gamma rays.

Gamma radiation used to destroy tumours

Gamma rays destroy cancerous cells , narrow beam minimises healthy cell damage.

Gamma can penetrate deeper into cell than others

Radioactive implants

An alternative method of using beta or gamma emitters to irradiate a cancerous tumour over a given time

Current

A flow of electrons

potential difference

the difference in electrical charge between two points in a circuit expressed in volts

Efficiency

The percentage of the input work that is converted to output work

The more resistance

It is harder for electrons to flow, therefore decreasing the current

Fuses

an electrical device that can interupt the flow of electrical current when it is overloaded

If the live wire touches the metal case...

... a large current flows to earth ( instead of you as the Earth wire has low resistance ) and melts the fuse, breaking the circuit.

Only electrons can

Be removed or added to an atom

Like charges

repel

Unlike charges

to attract

A charged object creates an ________ _____ around itself

electric field

Ballon on wall

Charge up balloon ( rub on clothes )

Negative electrons on the balloon repel the negative electrons in the wall surface- they move deeper into the wall leaving the surface of the wall positive so negative balloon attracts to positive wall

Van de Graaff generator

a device that uses friction to produce a large static charge on a metal dome.

Builds up negative charge as the high pd between the dome and the earthed conductor ( 0V) increased electrons jumped across the gap and caused a spark

Electric Field Lines are drawn

To show the way a positively charged particle would move