Physics - Yr11

How can energy be transferred between stores

Radiation mechanically heating electrically

What is a system

A collection of matter

What happens when the system changes

Energy is transferred (to different objects or forms)

What is an open system

When it can gain/lose energy with the outside world

What is a closed system

No matter or energy can enter or exit

Mechanical work

Force to move an object

Electrical work

When a current flows

Gravity

Force of attraction between two objects

Weight

The force acting on an object in a gravitational field

Total energy in a closed system

Never changes

What do unstable isotopes do

Decay into other elements by emitting radiation

Ionisation

When an electron gets knocked out forming a positive ion

Types of nuclear radiation

Neutrons alpha beta gamma

What is an alpha particle

A helium nucleus (2 protons 2 neutrons)

Why are alpha particles not very penetrating

As they are relatively large so collide and are easily stopped by other particles

How far can alpha particles travel in air

A few cm

What absorbed alpha radiation

A piece of paper

How ionising is alpha radiation

Strongly

What are beta particles

An electron

Charge of alpha radiation

2+

Charge of beta radiation

-1

How is beta radiation formed

When a neutron decays into a proton and electron

How ionising is beta

Moderately

How penetrating is beta

Moderately

How far can beta travel in air

Several meters

What absorbed beta radiation

5mm of Al

What are gamma rays

Electromagnetic radiation waves

How ionising is gamma

Weakly

How penetrating is gamma

Deeply

What absorbs gamma rays

Thick sheets of lead or several meters of concrete

What is activity

The overall rate of decay of all isotopes in the sample

Half life

Time taken for the number of radioactive nuclei to halve