The Student Room Group

Definition of resonance

Have a lot of varied definitions of resonance from textbooks and past paper markschemes...

Similarities of definition: driving frequence = natural frequency

Differences of definition: sometimes "resulting in large amplitude", sometimes "resulting in maximum amplitude", sometimes both - which is just confusing (from markscheme - large amplitude AND maximum amplitude - wth does that mean?).

Someone please clear the confusion! Thanks!
Reply 1
ive always understood it as maximum :s-smilie: but i suppose technically the max amplitude is large in proportion, may be why both are in the mark scheme
Reply 2
dh00001
ive always understood it as maximum


As have I.
Reply 3
This is how I define it: Resonance is when a forced vibration causes a system to oscillate at a particular frequency which is its natural frequency that results in a large energy transfer to the system and hence very large or maximum amplitudes occur.

The large amplitude occur because the actual frequency which the system vibrates at (when given a simple displacement and left) is applied by a generator or other force therefore it usually makes huge amplitudes, if not the maximum it can.
Reply 4
Resonance is when a system is induced to oscillate at its natural frequency by an external force, hence resulting in maximal energy transfere and large amplitudes of oscillation.

( I dont say maximal amplitudes because it depends on the dampening)
Reply 5
Wangers
Resonance is when a system is induced to oscillate at its natural frequency by an external force, hence resulting in maximal energy transfere and large amplitudes of oscillation.

( I dont say maximal amplitudes because it depends on the dampening)

Doesn't maximal energy transfer imply maximum amplitude, since

E is proportional to A^2?

I don't know but here's the Markscheme:

Resonance (each point one mark):

- When vibration is forced (or driven) at natural frequency

- Amplitude (or displacement or oscillation) is large (or violent or
increases)

- Amplitude is a maximum / large energy transfer



This is so vague and confusing!!
Reply 6
Seriously, exam boards should specify the definitions they want clearly! I mean - we don't have the time and energy to decipher what you want!!
Reply 7
I would think the second and third would simply be one mark. Just to be on the safe side, mention both in the exam.
Reply 8
i thought resonance was the frequency at which the energy transfer from a wave to a system was most efficient, i.e. haivng a high amplitude due to getting loads of energhy form a wave.
Reply 9
sufiankane
i thought resonance was the frequency at which the energy transfer from a wave to a system was most efficient, i.e. haivng a high amplitude due to getting loads of energhy form a wave.

Yes, we are on the same lines.
Reply 10
My teacher is a chief examiner for edexcel and he says that you must mention that this is the frequency at which MAXIMUM ENERGY TRANSFER occurs to get the mark. Maximum amplitude itself won't do.
Reply 11
From what I've seen in markscheme u have to mention (in bold):

A body that is forced to oscillate at its natural frequency, therefore has a maximum/largest/greatest amplitude/frequency/displacement and a large anergy transfer.

The reason why I have written maximum/largest/greatest is because the examiners want a clear comparison. You won't get the mark if you say big/large.
And remember examiners have to marks 100s of these papers, so they are looking for the right terminology
These questions usually carry only 2-3 marks top so you should be safe with this definition.
Reply 12
I don't understand what's so confusing about those two, they are both right...