Paper 2 - Weak Points

Question 1

Define Lenz’s Law

Answer 1

The direction of the induced emf produced by the changing flux linkage is such that it will oppose the direction of the flux that is producing it

Question 2

What are the five assumptions used in the derivation of the kinetic theory model of gasses?

Answer 2

1. The particles move randomly (Brownian motion
2. The particles experience no attraction to one another and there are no forces acting between them
3. The volume of the particles is negligible compared to the volume of the container
4. All collisions are perfectly elastic
5. The time taken for collisions is negligible compared to the time taken to cover the distance between them

Question 3

How do you find the point at which a body with mass does not experience a force when it is placed between two larger bodies that have gravitational fields?

Answer 3

Assume that the gravitational field strength due to both bodies is the same so set the equations equal and solve for r. If it is the distance from one body then one value is r and the other value is (total distance - r)

Question 4

Describe Newton’s Law of gravitation/Coulomb’s law in words

Answer 4

The force between two objects is proportional to their mass/charge and is inversely proportional to the squared distance between them (including their radius because you go from the centre of mass)

Question 5

What is a low polar orbit?

Answer 5

An orbit that has a time period less than that of a geostationary object because it is orbiting lower

Question 6

Why don’t satellites do work to move around a planet?

Answer 6

They travel along equipotential lines

Question 7

Define permittivity

Answer 7

How easy it is to create an electric field in a material

Question 8

What is a dielectric

Answer 8

A material that contains polar molecules that move to align themselves with the electric field meaning they oppose the electric field produced by each of the plates and increase the capacitance

Question 9

Why does the polarity of the D-shapes in a cyclotron need to change?

Answer 9

In order to accelerate the particle from one to the other over the gap

Question 10

What is the frequency of AC current needed in order to reverse the polarity of a D-shape in a cyclotron?

Answer 10

Equal to the frequency of the particle moving around it