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# Applied physics module 4,5,6

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## Pete Davis

on 12 November 2012

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#### Transcript of Applied physics module 4,5,6

1 – Static electricity
2 – Repulsion and attraction
3 – Electric circuits
4 – Circuit symbols
5 – Currents
6 – Resistance
7 – Thermistors and light dependent resistors
8 – Series circuits
9 – Parallel circuits
10 – Electromagnetic induction
11 – Electric Generators
12 - Power
13 – Transformers
14 – Energy
15 – Efficiency of appliances
Module P5
Electrical Circuits
Static electricity
Repulsion and attraction
Electric circuits
symbols
Current
resistance
Thermistors and LDR
Series and Parallel
Electromagnetic induction
Electricity generators
Power
Transformers
Cost of Electricity
Efficiency of appliances
Energy
The material receiving the electrons becomes negatively charged and the one giving up electrons becomes positively charged
Only works with
insulators
Positive
Negative
Like Charges repel
Opposites attract
A current is a flow of charges.
The battery causes the charges to move in a continuous loop around wires and components
In metal conductors, there are lots of charges free to move.
A direct current (d.c.) always flows in the same direction
An alternating current (a.c.) changes the direction of flow back and forth
The amount of current flowing in a circuit
depends on the potential difference (v)
across the components
The greater the p.d (voltage), the greater the
current that flows through the component.
The greater the resistance of a component,
the smaller the current that flows.
Resistance (ohms)
measures how hard it is to get a current through.
1st Equation !
As light resistance
LDR
As Temp resistance
Thermistor
Series
current the same voltage splits

Parallel
current splits voltage the same
Note: In parallel the more branches
the lower the overall resistance
of the circuit
In electromagnetic induction, movement of a magnet produces voltage
The size of the voltage can be increased by:
Increasing the speed of rotation
Increasing the strength of the magnetic field
Increasing the number of turns
Putting an iron core inside the coils
Only works with AC
An AC in the primary coil creates amoving magnetic field
in the core which induces a current in the secondary coil
Step down
step up 2nd > 1st
step down 2nd < 1st
2nd equation
Power (watts) = Current (amps) x Voltage (volts)
3rd eqaution
1 watt = 1 joule per second
energy transferred = watts x seconds
cost of eletricty = Kw x Hours x cost of a unit
4th equation
x 100
5th equation
6th equation
P4 Explaining Motion
Motion
Energy
Force
Some of the kinetic energy
is transferred to heat energy
Distance time graph
Speed time graphs
1. Speed
2. Velocity
3. Distance time graph
4. Velocity time graphs
5. Force Pairs
6. Resultant Forces
7. Momentum
8. Change in Momentum
9. Energy and Work Done
10. K.E and P.E
Area under graph = distance
solid surface - reaction
Liquid - upthrust
Air - lift
If forces are balanced
Force diagrams
The object is stationary
Forces come in pairs
Unbalanced forces = resultant force
a resultant force causes objects to change speed
Speeding up !
Slowing down !
Kg m/s = Kg x m/s
Change in momentum = Resultant Force x Time for the force to act
Kgm/s
Newtons
Seconds
Car Safety reduces force by
increasing
time
Seat belts
Air bags
Crumple Zones
Energy
Work done (j) = Amount of Energy Transferred (j)
Note !
Weight is a force
Weight on Earth (N) = Mass (kg) x 10
Kinetic energy is movement energy
(j)
(kg)
(m/s)
2
Gravitational Potential Energy = Weight x Height
(j) (N) (m)
Some KE is lost as heat
through friction
Series - Current
same
- voltage
splits
Parrallel - Current
splits
- voltage
same
This makes
AC
current
All actions cause
an opposite and equal
reaction
1. speed = d/t
2. acceleration = (v-u)/t
3. momentum = mxv
4. change in momentum = fxt
5. work done = fxd
6. work done = energy transferred
7. GPE = Weight x Height
8. K.E = 1/2 m(v) 2
9. weight = mass x 10 (on Earth)
electric motors
Movement
,
magnetism
,
current
P4 Motion
P5 Eletricity
P4 P5 P6
Isotopes-
same
number of
protons

different
number of
neutrons
remember in Ions
number of protons
is different to the
number of electrons
This can cause mutations
Alpha particles are helium nuclei
2 protons, 2 neutrons
Positive charge
very ionising
stopped by paper

when alpaha decay happens
atomic mass - 4
atomic number - 2
Beta is a high energy electron
negative charge
stopped by 5 mm Aluminium

Happens when a neutron turns into a proton and an electron

Atomic mass stays the same
Atomic Number goes up !

Nuclear Fission splits atoms
and is used for UK's
cuurent nuclear power industry

Rutherford's scattering experiment
The rutherford model

to sterilise surgical instruments
to kill harmful bacteria in food
to kill cancer cells (note that lower doses of gamma radiation could lead to cells becoming cancerous)
medical imaging (gamma and beta)