Paper 2 mistakes Flashcards
(47 cards)
Why are the properties of a radial gravitational field?
-Region in which a mass experiences a non-contact force
-Any change in potential depends on the initial and final positions not on the path taken
-Force is always attractive
-Field lines point towards the centre of mass
-Equipotential surfaces are spherical about the centre of mass
Define the internal energy of an Ideal Gas?
The sum of the kinetic energies of all of the particles in the gas.
How do you check is a relationship is exponential or not?
Check whether the dependent variable (y-axis) changes decreases by half in equal amounts of the independent variable (x-axis.)
Why is it better to use electron diffraction to estimate the size of the nuclear radius rather than alpha particle closest approach method?
-Electrons can get close to the nuclei as there is no electrostatic repulsion
-Strong Nuclear Force is not involved
-Free electrons are easier to accelerate
-Alpha particles only give us the distance of closest approach
-Using electrons gives us greater resolution as the wavelength can be made very small.
What does the electron diffraction pattern look like, electron intensity against theta?
Curved line showing a decrease in intensity as you increase theta.
A non-zero minimum
Why is the constant density of a nuclear radius derivation only approximate?
- The derivation assumes that the mass of the nucleus is A x mass of nucleon which is not true was they are ignoring the binding energy
-The Volume equation assumes that the nucleus is a perfect sphere
-Protons have a slightly different mass to neutrons
Why is it a good idea to slow the fission neutrons down in a reactor?
-This increases the probability that they will be absorbed by the Uranium nuclei
-Slow neutrons do less damage to the rector shielding/structure of the reactor
-Slow neutrons transfer thermal energy to the moderator atoms by collision
Why are element with a small nucleon number preferred as moderator materials?
The closer the mass or the moderator atoms is to the mass of the neutrons in the core the greater the portion of momentum and kinetic energy is transferred to the moderator atoms. This means fewer collision are required to slow the neutrons down to thermal speeds so make them into thermal neutrons.
What type of radiation should be used to measure the thickness of aluminium sheets no matter their thickness?
Beta-Minus Radiation
Transformer efficiency equation?
efficiency= useful power out (I secondary multiplied by V secondary)/
total power in (I primary multiplied by V primary)
What is true about the alpha scattering experiment?
-Due to foil only being one atom thick it can be assumed that the alpha particles are only deflected once
-Nuclei are more massive than Alpha particles which allows the alpha particles to be deflected by more than 90 degrees.
-Deflections of alpha particles by electrons are much smaller than defections due to nuclei.
Why is radioactive high-level waste stored deep underground?
In order to protect the workers from nuclides with a small decay constant.
What is the rate at which energy is transferred due to nuclear fusion?
Calculate change in mass per second (mass converted into energy per second kg/s) then do E=mc^2 to calculate energy this releases due to nuclear fission.
Assumptions in the Derivation of the Kinetic Theory Model?
- All collisions are perfectly elastic.
- Volume of the Particles is negligible compared to the volume of the container.
- Collision time is negligible /small compared to time between collisions.
-There are no forces between molecules except in collisions.
What are the SI Units of Electric Field Strength?
NC^-1 , Vm^_1 or kgmA^-1S^-3
Electrons are transferred to a conducting sphere, where are the excess electrons located?
They are equally spaced on the outer surface because they repel each other equally.
Why can a satellite not have a circular orbit around a planet if another planet exerts a gravitational force on the satellite?
The resultant force from the two forces of gravity is not centripetal towards H.
What is the function of the core in a Transformer?
The core provides a greater linkage of magnetic flux compared to an air core.
The core focuses/directs the magnetic field to the secondary coil and sot iron is used because it allows for magnetisation.
Purpose of the secondary coil in a Transformer?
The Secondary coil has changing magnetic flux passing through it. (Or is cutting magnetic flux.)
This induces an emf and it’s size depends on the number of coil on the secondary coil.
How do a certain material in the iron core increase efficiency?
Material in a insulator and sheets of this insulator are used to reduce the strength of the eddy currents so smaller emfs are induced in the core due to the laminations of iron being smaller.
Why is a certain moderate potential difference applied across the transformer lines?
If the potential difference I stop low the current will be too high meaning that the energy will be lost to surroundings by heating.VI you mention by heating
If the potential difference is too high then this creates insulation difficulties. What they are talking about is how what an insulator is is a material which when charge flows through it or heat no further electrons are released form the atoms to increase the conductivity. After a certain potential difference the atoms cannot hold onto their electrons so they breakdown and become conductors rather than insulators.
What is capital N in Physics?
Neutrons
For a nuclide to decay via Beta-Minus Decay hat must it have on the N/Z graph?
Must be neutron-rich/ have a high neutron-proton ratio
Decay via Beta-Minus Decay
What is an assumption if you are calculating the specific latent heat of fusion or vaporisation from a heater heating ice or a liquid?
That the temperature of the ice or liquid remains the same.
No heat is lost to the surroundings.
Heater is 100% efficient.
