# Physics 1

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• Created by: Esther
• Created on: 06-12-12 23:14

a) All objects emit and absorb infrared radiation.
b) The hotter an object is the more infrared radiation it
c) Dark, matt surfaces are good absorbers and good
d) Light, shiny surfaces are poor absorbers and poor
e) Light, shiny surfaces are good reflectors of infrared

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## Kinetic Theroy

a) The use of kinetic theory to explain the different
states of matter.
b) The particles of solids, liquids and gases have
different amounts of energy.

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## Energy transfer by heating

a) The transfer of energy by conduction, convection,
evaporation and condensation involves particles,
and how this transfer takes place.
b) The factors that affect the rate of evaporation and
condensation.
c) The rate at which an object transfers energy by
heating depends on:
■ surface area and volume
■ the material from which the object is made
■ the nature of the surface with which the object is
in contact.
d) The bigger the temperature difference between an
object and its surroundings, the faster the rate at
which energy is transferred by heating.

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## Heating and insulating bulidings

a) U-values measure how effective a material is as
an insulator.
b) The lower the U-value, the better the material is as
an insulator.
c) Solar panels may contain water that is heated by
radiation from the Sun. This water may then be used
to heat buildings or provide domestic hot water.
d) The specific heat capacity of a substance is the
amount of energy required to change the
temperature of one kilogram of the substance
by one degree Celsius.
E m c

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## Energy transfers and efficiency

a) Energy can be transferred usefully, stored, or dissipated, but cannot be created or destroyed.
b) When energy is transferred, only part of it may be usefully transferred; the rest is ‘wasted’.
c) Wasted energy is eventually transferred to the
surroundings, which become warmer. The wasted
energy becomes increasingly spread out and so
becomes less useful.
d) To calculate the efficiency of a device using:
efficiency
useful energy out
total energy in (100%)
efficiency
useful power out
total power in (100%)

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## Transferring electrical energy

a) Examples of energy transfers that everyday electrical
appliances are designed to bring about.
b) The amount of energy an appliance transfers
depends on how long the appliance is switched
on and its power.
c) To calculate the amount of energy transferred
from the mains using:
E P t
d) To calculate the cost of mains electricity given the
cost kilowatt-hour.

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## Generating electricity

a) In some power stations an energy source is used to heat water. The steam produced drives a turbine that is coupled to an electrical generator.
Energy sources include:
■ the fossil fuels (coal, oil and gas) which are burned to heat water or air
■ uranium and plutonium, when energy from nuclear fission is used to heat water
■ biofuels that can be burned to heat water.
b) Water and wind can be used to drive turbines directly.
c) Electricity can be produced directly from the Sun’s radiation.
d) In some volcanic areas hot water and steam rise to the surface. The steam can be tapped and used to drive turbines. This is known as geothermal energy.
e) Small-scale production of electricity may be useful in some areas and for some uses, eg hydroelectricity in remote areas and solar cells for roadside signs.
f) Using different energy resources has different effects on the environment. These effects include:
■ the release of substances into the atmosphere
■ the production of waste materials
■ noise and visual pollution
■ the destruction of wildlife habitats.

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## The National Grid

a) Electricity is distributed from power stations to
consumers along the National Grid.
b) For a given power, increasing the voltage reduces
the current required and this reduces the energy
losses in the cables.
c) The uses of step-up and step-down transformers in
the National Grid.

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## General properties of waves

a) Waves transfer energy.
b) Waves may be either transverse or longitudinal.
c) Electromagnetic waves are transverse, sound waves are longitudinal and mechanical waves may be either transverse or longitudinal.
d) All types of electromagnetic waves travel at the same speed through a vacuum (space).
e) Electromagnetic waves form a continuous spectrum.
■ microwaves – mobile phones and satellite television
■ infra red – remote controls
■ visible light – photography.
f) Longitudinal waves show areas of compression and rarefaction.
g) Waves can be reflected, refracted and diffracted.
h) Waves undergo a change of direction when they
are refracted at an interface.
i) The terms frequency, wavelength and amplitude.
j) All waves obey the wave equation: v = f
k) Radio waves, microwaves, infra red and visible lightcan be used for communication.

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## Reflection

a) The normal is a construction line perpendicular to the
reflecting surface at the point of incidence.
b) The angle of incidence is equal to the angle of
reflection.
c) The image produced in a plane mirror is virtual,
upright and latterally inverted.

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## Sound

a) Sound waves are longitudinal waves and cause
vibrations in a medium, which are detected as sound.
b) The pitch of a sound is determined by its frequency
and loudness by its amplitude.
c) Echoes are reflections of sounds.

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## Red Shift

a) If a wave source is moving relative to an observer there will be a change in the observed wavelength and frequency. This is known as the Doppler effect.
b) There is an observed increase in the wavelength of light from most distant galaxies. The further away the galaxies are, the faster they are moving, and the bigger the observed increase in wavelength. This effect is called red-shift.
c) How the observed red-shift provides evidence that the universe is expanding and supports the ‘Big Bang’ theory (that the universe began from
a very small initial point).
d) Cosmic microwave background radiation (CMBR)
is a form of electromagnetic radiation filling the
universe. It comes from radiation that was present
shortly after the beginning of the universe.
e) The ‘Big Bang’ theory is currently the only theory
that can explain the existence of CMBR.

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