2021 Paper 2 (19/02/2025)

Question 1

Dielectric constant?

Answer 1

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

Question 2

Polar molecules changing capacitance?

Answer 2

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

Question 3

Same capacitance and diametre is halved?

Answer 3

C=A 𝜀0𝜀r / d -> C= πD^2 𝜀0𝜀r / 4d -> 𝜀r ∝ 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

Question 4

Launching satelite from equator?

Answer 4

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 Earth’s rotation

Question 5

Comparing linear speeds of satelites?

Answer 5

In a higher orbit the linear speed is smaller. This is because:
mv^2 / r = Gmm / r^2 -> v = √GM/r -> v ∝ 1 √r . This means as radius otherwise orbit height increases the linear velocity decreases as a result

Question 6

Why must something be a vacum to allow constant temperature?

Answer 6

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