Physics

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Waves

- A wave is a movement of energy (without moving matter)

1)Transverse:
-Particles vibrate at 90 deg. to the direction of wave propagation
E.g. waves on water and light waves

2) Longitudinal Waves:
-Particles vibrate parallel to the direction in which the energy is being transferred
E.g. vibrations and sound waves

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Waves

Diagram:

Frequency: No. of complete cycles of the waves which pass a point in one second (Hz)

Wavelength: Distance between one peak and the next (M) A wave with a long wavelength has a low freq and vise-versa.

Amplitude: Height from one centre line to the top of a peak(M). A high amplitude means that the wave is carrying more energy

Time Period:Time taken for one full cycle of a wave to pass a point (S)

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Diagram:

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Diagram:

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Diagram:

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Total Internal Reflection

When light reflects from the surface of a plane mirror, the angle of incidence is equal to the angle of reflection

Diagram:

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The speed of sound

The range of human hearing:
- Sounds ranging from 20Hz up to 20,000Hz. Sounds below 20Hz are called Infra sound- sounds above are called ultrasound

Uses of Ultrasounds:
-Conduct Medical Scans
- Break up kidney stones
-Clean delicate items such as watch mechanisms

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Diagram:

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Uses and dangers of EM waves

All
-Transverse Waves and travel at 300 000 000m/s

Gammy rays are aimed at the tumour- the source is rotated so that only the circle tumour recieves a high dose (killed)

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Currents

- flow of charged particles (electrons)
- Must be a complete circuit made from conducting materials (metals)
- Water can conduct electricity but only at high voltages

Can be detected by using a bulb, an LED or an ammeter

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Series circuit

In a series circuit the current is the same at all points

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Parallel Circuits

The current from the cells is split up around the loops on the circuit. The first current you measure is the total of the next 3 measurements.

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Voltage (Potential difference)

Measure of difference in energy between two points in a circuit

The difference between voltage and current:
-Current is a measure of how many electrons pass a point in a second

-Voltage is a measurement of how much energy each electron has (This energy comes from being attracted to the + side of the cell and repelled by the - side)

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Diagram:

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Diagram:

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Ohm's Law

Resistance is a measure of how difficult electrons find it to flow through a circuit component. When the resistance is big, it is very difficult for electrons to flow and vice-versa. this means the bigger the resistance, the smaller the current (resistance is measure in ohms)

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Finding the resistance of a length of wire

Sketch of the graph:

Conclusion:
> Relationship:
-The longer the length of wire, the bigger the resistance (directly proportional)

How can you tell?
-The shape of a line is a diagonal (slanted upwards)

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Diagram:

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Fuses/Earth Wire/ Double insulating

Fuse:
-Safety devices
-Come in handy when a large unsafe current is flowing
-Get incredibly hot and melt- breaking the circuit

The Earth Wire:
- The earth wire is connected to the metal case of an appliance
-If a wire inside the appliance comes loose and touches the case, then the case is electrically live and could give the user an electric shock.
-Carries the current to the ground if a live wire touches the case
-The Earth wire has a low resistance and so a large current will flow and it will melt

Double Insulating:
- means the case is made of insulating plastic material

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Generating Electricity

1) Coal is crushed into dust

2) Coal dust is burned in a furnace

3) Water is heated to become steam

4) The steam burns in a turbine

5) The turbine turns a generator

6) Inside the generator a magnet and coil of wire produce electricity

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Energy changes in different power stations

Coal Powerstations:

Chemical > Heat > Kinetic > Electrical

Hydroelectric Powerstation:

Gravitational P.E > Kinetic > Electrical

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Renewable energy

Pumped storage are well suited to being used to sudden surges in the demand for electricity
> easily turn it on/off by opening/closing the gate

Diagram:

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Magnetic fields

Area around a magnet which magnetic material experience a force.
> The lines are closer together where the magnet is stronger
>Arrows show direction of the force on a magnetic North pole

Diagram of a Bar Magnet:

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2 Bar Magnets

Diagram of repelling: Like poles are repelling

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Uniform Fields

When opposite poles are close then the fieldlines are straight/parallel/and equally spaced
> Magnetic field is of the same strength at all points

Diagram:

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Electromagnetism

The right-hand grip rule: Direction of the field lines
> electric current flows through a wire, magnetic fields form around wire

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Diagram:

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EM Induction

- A magnetic field line cuts through a wire= a tiny voltage is induced
>If there is a complete circuit a tiny current will flow
> the size of the voltage ( and therefore current) depends on the number of magnetic field lines cuttign through the wire per second

We can make a bigger voltage by:
1) Having more fieldlines (ie stronger magnet)
2)Having more wires (e.g. by coiling up the wire or increasing no. of turns on wire)
3) Increasing the rate at which the magnet/wire moves

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Table:

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Isotopes

- groups of atoms with the same no. of protons in  the nucleus but different no. of neutrons
> same element but different mass

E.g.

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- isotope that is radioactive (because they have an unstable nucleus)
> can be because there are too many protons close to eachother in a large nucleus
> the nucleus throws parts of its self away to become more stable

Most things are slightly radioactive- but some are more than others
>Rocks (especially graphite)
>The Sun
>Cosmic Rays

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Artificial: Nuclear power stations> Nuclear fallout>Nuclear waste> Medical uses

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Examples:

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Examples:

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Examples:

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