# physics p1

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## ENERGY TRANSFER

• Energy can be transfered or dispersed but cannot be destroyed
• Only part of the energy is useful, the rest is wasted
• The wasted enrgy spreads out and becomes less useful

efficiency - useful energy/total energy in (x100)

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## TRANSFERING ELECTRICAL ENERGY

• the amount of energy transfered depends on the power and time it is on
• E=pxt
• E= energy in kilo-watt hours (kWh)
• p= power in kilo-watts (kW)
• t= time in hours(h)

OR

• E=energy transfered in joules (J)
• p=power in watts (W)
• t= time in seconds(s)
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## WAVES

• transverse or longitudinal
• electromagnetic waves are transvers
• soundwaves are longitudinal
• mechanical waves can be either transverse or longitudinal
• longitudinal waves show areas of refraction and compression
• waves can be reflected, refracted and diffracted
• waves change direction when they are refracted
• v=fxw
• v= speed in metres per second (m/s)
• f= frequency in hertz (hz)
• w= wavelength in metres (m)
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## REFLECTION

• the normal is a construction line perpendicular to the reflecting surface
• the angle of incidence is equal to the angle or reflection
• the image produced in a plane mirror is virtual, upright and laterally inverted
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## SOUND

• sound waves are longitudinal
• sound waves cause vibrations detected as sound
• pitch is determined by frequency
• loudness is determined by amplitude
• echos are reflections of sounds
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• all objects emit and absorb infra-red
• the hotter an object the more infra-red emitted
• dark, matt surfacers are good absorbers and emitters
• light, shiny surfaces are poor absorbers and emmiters
• light, shiny surfaces are good reflectors of infra-red
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## HEATING AND INSULATING BUILDINGS

• U-values measure how effective an insulator is
• the lower the u-value the better the material
• solar panels contain water heated by the sun; used to heat buildings and as hot water
• specific heat capacity is energy needed to raise temp by one degree of a one kilo sample
• E=mxcxt
• E = energy transfered (J)
• m = mass (kg)
• t = temperature change (degrees)
• c = specific heat capacity (J/kg C)
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## ELECTRO-MAGNETIC WAVES

• all types travel at the same speed through a vaccum
• Form a continuous spectrum

Radio waves, microwaves, infra-red radiation, visible light, ultra violet, x-rays, gamma rays

• radio waves, microwaves, infra-red and light can be used as forms of communication
• microwaves - mobiles and satellite t.v.
• infra-red - remotes
• visible light - photos
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## RED SHIFT

• the doopler effect is the change in wave length and frequency observed when a wave source is moving relative to an observer
• wave source could be light or sound or microwaves
• as it moves away wavelenght increases and frequency decreases
• as it move towards wavelength decreases as frequency increases
• the further a way a galaxy is, the faster it is moving, the more red-shift is detected
• Red shift supports the 'Big bang theory'
• cosmic microwave background radiation comes from the radiation present shortly after the universe began
• 'Big bang theory' is only theory that supports CMBR
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