Key relationship
fwire=(1/2L)√(T/μ); attraction repeats twice per AC cycle, so fAC=fwire/2.
Physics · Practical apparatus
AC sonometer resonance
Tune the bridge spacing while keeping tension and density fixed. Resonance occurs when the wire natural frequency matches the force frequency. An unbiased AC electromagnet attracts on both current polarities.
Open the interactive experiment →AC sonometer resonance
கம்பியின் நீளத்தை மாற்றி ஒத்ததிர்வைத் தேடவும். மின்காந்த ஈர்ப்பு ஒரு AC சுற்றில் இருமுறை நிகழும்.
Key notes, relationships and model limits
Practical tip
Tune the bridge spacing while keeping tension and density fixed. Resonance occurs when the wire natural frequency matches the force frequency. An unbiased AC electromagnet attracts on both current polarities.
Common trap
Do not equate wire frequency with mains frequency for this attraction setup.
Model limits
Fundamental stretched-wire mode; constant tension; ideal electromagnet attraction proportional to current squared. Damping ratio0.03 creates a finite resonance response. Virtual frequency only.
What you will learn
Infer virtual AC frequency from wire resonance.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
L1 m,T40 N,μ0.001 kg/m gives100 Hz wire and50 Hz AC.
Why this matters
The model connects ac sonometer resonance with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
At resonance the wire is100 Hz. The AC supply is?
- 100 Hz
- 50 Hz
- 200 Hz
Read the explanation
Attraction has two peaks per AC cycle, so divide by2.
Course connection: Virtual apparatus preparation. Check exact board/exam membership in the syllabus sources. Physical practical work remains necessary.