Mock Questions

Question 1

Explain in terms of particle behaviour why the resistance of the nichrome wire changes as temperature increases

Answer 1

Kinetic energy energy of ions increases

Frequency of collisions between electron + ions

Drift velocity of electrons decrease so current decreases

So resistance of nichrome wire increases

Question 2

Describe why a plank on top of a rock will tip if she walks from one side to the other

Answer 2

Plank will topple when clockwise moment is greater than anticlockwise moment

(Show using numerical values x > y)

Question 3

Bulbs are connected in parallel, another bulb is added
Explain why the bulbs will get dimmer and temperature of bulbs increase as more bulbs are added (6marks)

Answer 3

The resistance of circuit decreases as more bulbs are added so current increases
Therefore voltage increases
Terminal pd decreases and bulb gets dimmer
More energy transferred in battery
So thermal energy increases

Question 4

What is meant by critical angle

Answer 4

The greatest angle at which there is a refracted ray in a less dense medium

Question 5

Describe how light would travel through a crystal

Answer 5

Light strikes crystals at engles greater than the critical angle
Light is then constantly internally refracted along the crystal

Question 6

What is meant by super position of waves

Answer 6

The interaction of two or more waves where the resultant displacement is the sum of the individual displacement of the waves

Question 7

Explain why only certain wavelengths of light are emitted in a spectra

Answer 7

Atoms can only exist at certain energy levels
As atoms gain energy they get excited
And move to higher energy level
As they emit a photon they drop energy levels
Releasing photon
The wavelength of this photon is dependant on the energy of the proton