P2 Fc Before Exam

Question 1

Define electromotive force

Answer 1

Electro motor force is the work done per unit charge

Question 3

Give an equation for calculating the permittivity of a material

Answer 3

C=er x eo x A/ d
Capacitance = relative permiativity x permiativity of air x area / distance between plates

Question 4

How do we find the maximum EMF from a magnetic flux linkage against time graph

Answer 4

Draw a tangent where the gradient is the greatest as EMF is proportion to the rate of change of flux linkage then find the gradient of the tangent

Question 6

Define a Tesla

Answer 6

The flux density which produces a one newton force on a 1 m long wire carrying one of current flowing perpendicular to the field

Question 8

Describe the path of a charged particle entering at right angle to a uniform magnetic field

Answer 8

Circular

Question 10

Explain the two rolls of the core in a transformer

Answer 10

The core directs the magnetic field round to the secondary coil and ensures that more of the flux from the primary coil linked with the secondary coil

Question 11

Explain two features of the core and a transformer which aids the efficiency of the transformer

Answer 11

It is made from soft iron so that it can be easily magnetised and demagnetised and it is laminated to increase resistance and reduce current

Question 13

Define electric potential at a point

Answer 13

The work done per unit +ve charge on an object to bring it from infinity to that point

Question 14

How do you find the electric potential between 2 charges at the midpoint

Answer 14

Find the electric potential for one at the midpoint, do the same for the other
Then add the two potentials
Remember the charge for an electron = - 1.6…

Question 15

Explain why a high speed proton is required to fuse with a nucleus

Answer 15

The proton is repelled by +ve nucleus therfore a high speed proton will gat close enough to nucleus to fuse

Question 16

How do protons stay within a nucleus

Answer 16

Due to the strong nuclear force that acts on the protons and is attractive

Question 18

What material is required to absorb a beta particles?

Answer 18

3 mm aluminium

Question 19

What is a photon

Answer 19

A discrete packet of electromagnetic energy

Question 20

Describe a reasonable value for the half-life of the tectinium 99M isotope which is used as a medical tracer

Answer 20

Six hours

Question 21

Tech technetium- 99m has a half-life of six hours calculate the fraction of the initial number of nuclei that remains after 24 hours

Answer 21

Fast find the number of half-life in 24 hours which is( 24 divided by 6)
Then do 0.5 to the power of the number of half life which gives you a 16th to show the fraction of the initial number of nuclear that remains?

Question 23

Define activity

Answer 23

The rate of decay of a nuclei

Question 24

Give an equation to find the initial rate of energy emission of a substance subs at

Answer 24

E of photon x activity