2021 Paper 2 (19/02/2025) Flashcards
Dielectric constant?
The permitivity of the dielectric constant is the value of the dielectric constant times the permitivity of free space. Otherwise, the dielectric constant is the ratio of permitivity of a medium divided by the permitivity of free space being equal to the value of the dielectric constant
Polar molecules changing capacitance?
Polar molecules allign with the field lines meaning their positive side attracts to the negative plate and their negative side attracts to the positive plate. This proudces a counter electric field which reduces the field between the plates. Since its an isolated charge it stays constant and voltage decreases resulting in capacitance increasing due to C=Q/V but this is only the case since its not attached to the power supply battery. But, if it was then voltage would stay constant and charge would decrease which decreases capacitance
Same capacitance and diametre is halved?
C=A π0πr / d -> C= ΟD^2 π0πr / 4d -> πr β d/D^2. To get the same capacitance and halving the diametre results in relative permitivity being multiplied by 4 by inserting a dielectric equal to a relative permitivty of 4. As well the distance between the plates should decrease by a factor of 4 which is a quarter of original distance
Launching satelite from equator?
It should be launched at the equator with some speed due to at this position the satelite having the largest initial speed otherwise kinetic energy from the Earthβs rotation
Comparing linear speeds of satelites?
In a higher orbit the linear speed is smaller. This is because:
mv^2 / r = Gmm / r^2 -> v = βGM/r -> v β 1 βr . This means as radius otherwise orbit height increases the linear velocity decreases as a result
Why must something be a vacum to allow constant temperature?
If not in a vacuum gas atoms will collide with air atoms changing their directions or speed distribution which consequenly changes the energy and resulting in there being no constant temperature
Pressure decrease with less particles?
Pressure is due to collisions of particles with walls. With less particles there is a lower frequency of particle collisions per second. Since average momentum change per collision stays the same it means the total momentum change per second decreases which is why pressure lowers. In the equation: pv = 1/3 N m crms^2. Since crms is constant from constant temperature it means number of particles is directly proportional to pressure.
Higher temperature and collision patterns?
The higher temperature means particles are travelling faster. Since they are travelling faster it means they arrive at the detector quicker meaning the pattern is shifted to the side which is closest.
EMF effect when distance to search coil increases?
As the search coil moves there is a rate of change of flux through the coil. However, since its moving further away the magnetic field strength decreases, this means the rate of change of flux decreases. As induced EMF is proportional to rate of change of flux it means that since this decreases them EMF will also decrease
Proton having a semicircular path in dee of cyclotron?
Force due to uniform magnetic field is constant and at 90 degrees to the direction of travel. Since it is perpendicular it means the force will be centripetal for this circular otherwise semicircular motion
Fundamental of accelerating charged particles?
Anything with a charge of +- e otherwise +- 1.6x10-19 is accelerated at 1V its energy will be equal to 1eV
Why can energy be released when two nuclei undergo fusion?
When nuclei fuse their mass decreases which highlights the mass of the nuclei is more than the mass of the product of fusion. The binding energy per nucleon increases when a nucleus is formed from fusion so the difference in binding energy is the energy that is released
How to go from βuβ into energy?
βuβ goes into energy by multiplying the value of βuβ by 931.5. This gives the magnitude of βuβ the units of MeV
Nucleus affecting rate of fusion?
Increasing the charge increases potential energy otherwise force to bring nuclei together due to E = 1/4πΞ΅0 Qq/r. This increases in potential energy means more KE and pressure of fusion which consequently decreases the rate of fusion. A larger radius requires smaller amounts of KE otherwise pressure of fusion, leading to greater separation distance which increases the rate of fusion. A larger nucleon number is why the nuclear radius is larger and this is due to R=R0 A^1/3.
How to calculate root mean square speed?
β(u1^2 + u2^2 + β¦ ) / total number of particles
Equipotentials, Field Lines and Work Done?
An equipotential should have no work done across it whereas field lines require work done across it
Properties of main electricity?
The mean voltage is 0V. The peak voltage is 325V. Peak to Peak Voltage is 650V. RMS Voltage is 230 V.
Purpose of moderator?
To decrease neutron speeds to allow them to be absorbed by the fuel rods
