Definitions Flashcards
(23 cards)
What is the specific latent heat of fusion?
The energy required to change the state of 1 kg of a substance from the solid state to the liquid state without a change in temperature.
What is the specific latent heat of vaporisation?
The energy required to change the state of 1 kg of a substance from the liquid state to the gas state without a change in temperature.
Electric Field strength at a point in the field?
The force which a unit positive charge experiences at that point in the field.
Textbook answer:
Force per unit positive charge.
Gravitational field strength?
The Force which a unit mass experiences st that point on the field.
Gravitational potential?
The work done in moving a unit mass from infinity to that point in the field.
Electric potential?
The work done in moving a unit positive charge from infinity to that point in the field.
Why does a pump with a higher power and a heater raise the temperature of the same amount of water in the same amount of time by more?
The pump does more work on the water
So the work done by the heater and the pump both raise the temperature of the water.
The thread breaks.
Explain the motion of the ball.
[2 marks]
The ball experiences a constant electrostatic force of repulsion horizontally away from the wall.
Ball experiences a constant gravitational force directly/vertically downwards.
So ball experiences a constant resultant force and therefore constant resultant acceleration.
What does a capacitance of 370 microfarads mean?
A capacitor that stores 370 micro-coulombs of charge for every 1 volt of potential difference across the capacitor’s plates.
LOOK AT the UNITS OF CAPACITANCE, MICRO or KILO ETC, That is also the units of charge stored per 1 volt.
Lenz’s Law?
The direction of the induced EMF when there is a change in flux linkage is such that it will oppose the change causing it.
How is Lenz’s Law demonstrated?
A North/South Pole is induced on the LHS/RHS of the coil.
This opposes the motion of the bar magnet because the to North/South poles repeal each other.
What type of radiation Is used for sterilising medical equipment?
Gamma radiation because it is the most penetrating.
Why does Alpha, Beta or Gamma radiation not cause the surfaces which it comes into contact with to become radioactive?
Alpha, Beta and Gamma Radiation are ionising radiation which does not affect the nucleus. For a material to become radioactive the nucleus must be affected which ionising radiation (Alpha, Beta, Gamma) does not do.
Why might a source of radiation not follow an inverse-square law?
- Dead-time in the GM Tube detecting the radiation.
- Assumes no absorption between the source and the detector.
-Source is not a point source.
-Distance d between the source and the detector may not be the real distance between the source and point of detection.
When using the half-life equation what must you remember?
t1/2=ln2/Lambda(decay constant)
The half-life time which you calculate will have the same units as the decay constant so if decay constant in years^-1 then half-life is in years also. Seconds, seconds also.
What does the SNF act between?
The SNF acts between all nucleons, so all neutrons and protons
What does the electromagnetic/electrostatic force act between in the nucleus?
Protons
In large nuclei why are there more neutrons than protons?
More neutrons are required to hold the nucleus together (to increase the distance between the protons so decrease the electrostatic repulsion force between the protons so that the SNF can balance out the electrostatic repulsion force and hold the nucleus together.)
To add to the binding Force.
What must you remember when writing decay equations?
Must always put the Atomic number and mass number of electrons( Beta-Minus particles) also.
The thallium nucleus is formed in an excited state. Electromagnetic radiation is emitted from the thallium atom following its formation.
Explain the origin and location of two sources of this radiation.
The electrons orbiting the nucleus emit energy as EM radiation(Gamma Radiation) and de-excite to lower energy levels in the atom.
Why so 99 43 Tc (Technetium-99m) a suitable source of radiation for medical diagnosis?
Technetium-99m
- Emits only gamma radiation
-Gamma rays are weakly ionising
-Has a half-life which allows tests to be carried out but is short enough to limit exposure so reduce harm to body tissue.
-Can be prepared close to or in the hospital.
