Energy Flashcards
definition of energy
‘the ability to do work’
SI unit for energy
joule (J)
non SI unit of energy
electronvolt (eV)
What is 1 eV equivalent to
1.6 x 10^-19 J
which is the most convenient way of expressing energy in Radiography, and why
the electronvolt as you will encounter it in the form of Kev (a thousand or 10^3 eV) or Mev (a million or 10^6 eV)
what is power
the rate at which energy is used or produced:
i.e energy (joules)/time (seconds)
SI unit of power
watt
what is 1 watt equivalent to
1 joule of energy per second
what does the low of conservation of energy state
that ‘the total amount of energy (or mass) in a closed system remains constant’
or
‘energy cannot be created or destroyed, but can be converted from one form to another’
6 common forms of energy
mechanical thermal chemical electrical radiant nuclear
what is mechanical energy
the energy that an object possesses by virtue of its motion of position
there are two common forms of mechanical energy. what are they?
1) Energy of a moving object
2) Energy of an object by virtue of its height in a gravitational field
how would you calculate the energy of a moving object
Kinetic energy (KE) calculated by KE= 0.5 x m x v^2 (where m is mass of object and v is velocity
how would you calculate the energy of an object by virtue of its height in a gravitational field
Potential energy (PE) calculated by PE= m x g x h (where m is mass of object, g is acceleration due to gravity and h is its height above a reference level)
what is thermal energy
commonly referred to as heat. Results from the movement or vibrations of the molecules within an object.
the faster the atom and molecules in a substance vibrate, the more thermal energy the substance has and therefore…
the higher its temperature
What is chemical energy
energy that is stored within elements and compounds
what is electrical energy
that which can be used to enable an electron to move within a given system
what is radiant energy
those such as x-rays, gamma rays, light, microwaves, radio waves which are propagated through space as photons, or waves of electromagnetic radiation.
grouped togetehr as the electromagnetic spectrum
what is nuclear energy
that which is stored up within atoms
example of nuclear energy
in the sun, hydrogen nuclei fuse together to make a helium nuclei, in a process called fusion which releases energy.
or in a nuclear reactor, uranium nuclei split apart, in a process called fission.
