Practice with phasors
Question 30W: Warm-up Exercise		

Phasors are useful tools which help you to understand how waves superpose at a point. They become essential in chapter 7 so it is best to get really confident with them at this stage!
Superposition of waves using phasors
In each of the cases below, add the two phasors and draw (accurately!) the resulting phasor. Draw the larger circles with 1 cm radius (2 cm diameter). Draw the smaller circle with 0.5 cm radius (1 cm diameter). 

Linking phasors to waves
Look at the sketch graph below:

For points A, B, C and D draw the corresponding phasors in the circles below:

	5.	How big is the angle in each case?
 0: Zero              A:                   B:                    C:                         D:                    

The diagram below shows waves A, B and C:

From the diagram, give the phase differences between:
6.	Waves A and B 

7.	Waves A and C 

8.	Waves B and C

If the amplitude of wave A is 1 cm, give the amplitudes of:
9.	Wave B: 

10.	Wave C: 

You have seen
1.	That spinning arrows, called phasors, can help you to understand waves and their relative phases.