What is the energy source for starts
Fusion
Describe fusion
The creation of a larger nuclei resulting in a loss of mass from smaller nuclei, accompanied by a release of energy
Explain why the activity of a radioactive sample decreases with time
- activity is due to a nucleus decaying
- after some time fewer radioactive nuclei are left
- so number of decaying nuclei per second decreases
Explain how scientists can use radioactivity to find the age of the piece of granite
- there is a known activity when rocks are formed
- measure the activity now
- compare original activity to now
- determine number of half lives elapsed
- calculate age from number of half lives
Explain the role of the moderator in a fission reaction
- reduces the kinetic energy of the neutrons
- which allows fission to continue as neutrons can be absorbed by uranium
what is the principle of moments
if an object is balanced, the total clockwise moment about a pivot equals the total anticlockwise moment about that pivot
describe how a photocopier uses electrostatics
- the drum is given a positive charge
- the image that is to be copied is projected onto the drum
- light is shone past it so that all the areas not covered by the image lose their charge
- negatively charged toner is sprayed onto the barrel and is attracted to the opposite charge
- paper is placed on top and is heated to melt the toner in place
how do inkjet printers ork
similarly to photocopiers except they use a small jet of coloured ink which is negatively charged
what is the scale for the absolute magnitude of stars
the brighter the star, the smaller the magnitude and it does go into minus numbers
explain the term galactic redshift
- an increase in the observed wavelength of light emitted from DISTANT galaxies
- when compared to the wavelength of similar light on earth
- galactic redshift is evidence that the universe is expanding
explain why galactic redshift provides evidence to support the big bang
- because if the universe is expanding then it must have been closer together in the past
- the expansion of the universe can be reversed back to a single point of origin
describe and explain what can be deduced from the cosmic background radiation
- microwave radiation is observed at all points in space around the universe
- this radiation was produced when the universe was formed
- the wavelength of the radiation has expanded over the years to be in the microwave region of the em spectrum but initially it would have been high energy towards gamma
- this is evidence that the universe has expanded
state and explain what type of electromagnetic radiation the CMBR will change into over the next few billion years
- radio waves
- since the universe continues to accelerate outwards
- therefore the wavelength of the CMBR increases
state why our understanding of the beginning of the universe is just a theory
- there is no physical evidence to check
- because the temperatures are too high to reproduce
what is the structure of a transformer
consists of a primary coil and a secondary coil wrapped around an iron core
what is a transformer used for
increasing or decreasing the potential difference of an alternating current
what is the coil set up on step-up and step-down transformers
step-up - increases the potential difference so has more turns on the second than the first
step-down - decreases the potential difference so has more turns on the first than the second
what are step -up and -down transformers used for
step up is used to as to transport electrical energy at high voltages
step down is used to lower voltage for the use in homes
also used in adapters so the voltage is low enough for appliances
