3.3.1.2.1.4.2 A measure of how fast or
slow an object is moving
3.3.1.2.1.4.3 Q
3.4 A,Z,X notation
3.4.1 The number of protons in the nucleus
is called the proton number, Z
3.4.1.1
3.4.2 The number of protons plus the number of
neutrons is called the nucleon number, A
3.4.2.1 The values of Z and A are often shown using
A,Z,X notations, where X is the chemical symbol
for the atom in question
4 Electricity
4.1 Circuits
4.1.1 Series
4.1.1.1 Current is the same at
any point in the circuit
4.1.1.2 All the components in a
series circuit have the same
current flowing through them
4.1.1.3 The total potential difference of the cells
is the sum of the individual cells
4.1.1.4 The potential difference of the supply is
shared between the components
4.1.1.5 The total resistance is the
sum of all the individual
resistors or components
4.1.1.6 Can only follow 1
pathway or course
4.1.2 Parallel
4.1.2.1 The current splits when it reaches a
junction
4.1.2.2 No current is lost at a
junction
4.1.2.3 Total current into the junction=
total current out of the junction
4.1.2.4 Christmas tree lights
4.1.2.5 Houses use Parallel circuits
4.1.2.6 Most house lights use Parallel
circuits
4.1.2.7 Safer
4.1.2.7.1 The voltage is the same for all
components
4.1.2.7.2 Each part of the circuit can be protected by its own
fuse or circuit breaker and controlled by its own
switch
4.1.2.8 Easier to add new
circuits
4.1.2.8.1 Easy to work out the total current being
drawn by the different parts of the circuit
4.2 Voltage
4.2.1 The voltage across components in a circuit
is measured in volts using a voltmeter
4.2.2 Voltmeters are always connected in
parallel across components
4.2.3 In parallel circuits the voltage is the
same across each of the bulbs
4.2.4 The resistance of a variable
resistor can be changed, in
order to vary the current
through, and the voltage
across, a fixed resistor
4.2.4.1 For fixed resistors (and wires at a constant
temperature), voltage and current are proportional to
eachother-- doubling the voltage will double the current
4.2.4.1.1 Resistors
4.2.4.1.1.1 For components such as filament
lamps, the resistance changes
with current. The resistance of a
filament lamp increases with
current, so the slope of the
voltage-current graph increases
4.3
4.4 George Ohm
4.4.1 The current, voltage and resistance of
electrical and electronic components
are related to each other. The physicist
George Ohm investigated this in 1827
4.4.2 We summarise his findings using the equation;
current, I (amps)= voltage, V (volts) / divided by
resistance, R (ohms). I= V / (divided by) R
4.4.2.1 This equation can be used to calculate
any one of the three variables, provided
that we know the other two
4.4.2.1.1 Example question... A
20 ohm fixed resistor
has a voltage of 12V
across it. Calculate
the current through it
4.4.2.1.2 Answer: I=V /
divided by R = 12 /
20 =0.6A
4.4.2.1.3 George Ohm
5 Graphs
5.1 Distance-Time graphs
5.1.1 Used to show the distance and
time taken in a journey
5.1.2 An increasing in gradient straight line
means the object is going at a steady speed
5.1.3 Flat sections mean the object
is motionless, ie stopped
5.1.4 To find the speed of an object
there are two methods...
5.1.4.1 Use the formula; Distance/time
(/ meaning divided)
5.1.4.2 Look at the area under the section of the graph you are
calculating the speed of and then apply the formula.
5.2 Velocity-Time graphs
5.2.1 Shows the velocity and the
time taken of an object
5.2.2 To calculate the acceleration use the equation;
Final Velocity-Initial velocity / (divided by) time
5.2.3 acceleration measured
in m/s squared
5.2.4 A - sign in front of the final answer
for acceleration indicates that it is
deceleration
5.2.5 An increasing gradient on the graph indicates steady acceleration
5.2.6 A flat section indicates steady velocity
5.2.7 The steeper the gradient of an increasing
line, the greater the acceleration
5.2.8 A decreasing gradient indicates
deceleration
6 Radioactivity
6.1 Nuclear Radiation
6.1.1 Some types of atom are radioactive
6.1.1.1 This means that the nucleus of the atom is unstable
and can break apart, emitting ionising radiation
6.1.1.1.1 This can be in the form of alpha,
beta or gamma radiation
6.1.2 Remember; When we talk about radioactivity or nuclear radiation,
it's radiation that's coming from the nucleus of the atom
6.2 See inside the Nucleus
6.3 Alpha
6.3.1 Alpha particles are helium nuclei
6.3.2 They are the most ionising
and least penetrating form of
nuclear radiation
6.3.3 They are absorbed by a thin
sheet of paper or by skin
6.3.4 Can cause concern within the public
becuase if the alpha particles are
absorbed by the skin, they can ionise
cells in your body
6.3.5 An alpha particle is made of
2 protons and 2 neutrons
6.3.6 An alpha particle is made up
of the same amount of
protons and neutrons as a
helium particle
6.3.6.1 An alpha particle
has a charge of 2+
6.3.6.1.1 An alpha particle
has a mass of 4
6.3.6.2 In an electric field, alpha is deflected
slightly towards the negative plate
6.3.6.3 In a magnetic field Alpha is deflected
slightly and opposite to beta
6.3.7 Alpha radiation can travel a few cm's in air
6.3.7.1 Alpha radiation can
be absorbed/stopped
by paper/skin
6.4 Beta
6.4.1 A beta particle is
ejected from the nucleus
6.4.2 A beta particle is
made of an electron
6.4.3 The charge of
this particle is -1
6.4.4 The mass of this particle is
so tiny that we count it as 0
6.4.5 Beta particles can travel
up to a metre in air
6.4.6 Beta particles can be
absorbed/stopped by a
few (around 5)
millimetres of aluminium
6.4.7 In an Electric Field, a Beta particle is very
deflected toward the positive plate
6.4.8 In a magnetic field,
a Beta particle is
deflected most
6.5 Gamma
6.5.1 A Gamma wave is an electromagnetic wave
6.5.2 Gamma waves have no mass or charge
6.5.3 Many resources have claimed that Gamma Waves can
range over many km in air, or could even be unlimited
6.5.4 Gamma waves can be absorbed/stopped by a few cms of lead or a few feet of concrete
6.5.4.1
6.5.4.1.1 Beta Decay
6.5.4.1.1.1 A beta particle is an electron
6.5.4.1.1.2 When an unstable nucleus
emits an electron, a neutron in
its nucleus changes into a
proton and an electron. The
electron is emitted
6.5.4.1.1.3 For example
6.5.5 In an electric field Gamma waves are not deflected at all
6.5.6 In a magnetic field, Gamma waves are not deflected at all
6.5.7 Gamma rays are the least ionising and the most penetrating
6.6 Half Life
6.6.1 The decay of every radioactive material follows the
same pattern. The activities and the half-lives may be
very different, but the shape of the decay curve is
always the same
6.6.2 There are two definitions of Half Life
6.6.2.1 1.The time it takes for half
the number of atoms in any
sample to decay
6.6.2.2 2. The time it takes the count
rate from a radioisotope to
decrease by 50%
6.6.3 Example; A radioisotope has
a half life of 12 minutes, what
fraction of the radioisotope
will be left after 1 hour?
6.6.4 Example Questions answer: 1/32
6.6.5 An Isotope is an element with the
same number of protons but a
different number of neutrons
6.7 Alpha Decay
6.7.1 When an unstable nucleus emits an alpha particle it loses 2 protons and 2 neutrons
6.7.1.1 For example; Radium-226 decays by alpha
emission, 226/88 Rn --> 222/86 Rn+ 4/2 He
6.7.2 Note: The atomic and mass numbers
on both sides of the equation balance
6.7.3 An Alpha particle is emitted in Alpha decay
6.7.4 A,Z,X notation; A decreases by 4, Z decreases by 2