phys notes

PHYSICS NOTESFOR IGCSE

By Sarah Jamil

30 April 201204:58 PM

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General Physics

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Thermal Physics

Radiation- energy spreading out from a source carried by particles or wavesConduction- transfer of heat or electrical energy through a material without it movingConvection- transfer of heat energy through a material by movement of the material

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Wave properties

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ROY

G

BIV

Reflection – a wave bouncing off a surface.Refraction – a wave changing direction when it passes from one material to another..Diffraction – a wave spreading out when it passes through a gap. Diffraction only occurs if the size of the gap is about the same as the wavelength of the waves.

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Electricity and Magnetism

When the light intensity decreases the resistance increases so the voltage increases so the light turns on.

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AC GeneratorMade up of insulated copper wire and is rotated by turning the shaft. The slip rings are fixed to the coil and rotate with it. The brushes are two contacts which rub against the slip rings and keep the coil connected to the outside part of the circuit. They are usually made up of carbon.

When the coil is rotated, it cuts magnetic field lines, so an e.m.f. is generated and electric current flows. As the coil rotates, each side move continuously upward and downward, in side the magnetic field. So the electric current flows backward and forward (Alternating Current).

The magnitude of induced electric current increases by increasing the following factors.

Increasing the number of turns in the coilIncreasing the area of the coilUsing a stronger magnetRotating the coil faster

DC Motor

A simple electric motor can be built using a coil of wire that is free to rotate between two opposite magnetic poles. When an electric current flows through the coil, the coil experiences a force and moves.The direction of the current must be reversed every half turn, otherwise the coil comes to a halt again. This is achieved using a conducting ring split in two, called a split ring or commutator. A coil of wire is used with lots of turns to increase the effect of the magnetic field.

How a transformer works

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When AC is supplied to the primary coil it induces a rapidly changing magnetic field which passes through the soft iron core to the secondary coil where it cuts the coil, inducing EMF. To increase the EMF increase the turns of the coil.

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Atomic PhysicsAlpha Beta Gamma

Ionising effect Strong Weak Very weak

Penetrating effect Not much

More than alpha Very penetrating

Behaviour in electric and magnetic fields Deflected

Deflected in opposite direction to alpha

Not deflected

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