AQA exam Board standing waves (alternate)

karen b

COMMITTEE
I haven’t seen this alternative, but in a previous role there was a similar experimental set up that used copper wire
 

Nick Mitchener

COMMITTEE
I have not seen that, but I did trial using the wire in a field way when the specification was first produced. It needs to be a resistance wire to prevent damage to the sig gen. 28 swg nichrome is about 10-11 ohms per metre so that would be fine.

That drawing of the layout is really bad, the wire is clamped but the string is just going to pull the vibration gen towards the bench pulley. The string should go through the stem of the vibration gen to a fixed point.
 
I have not seen that, but I did trial using the wire in a field way when the specification was first produced. It needs to be a resistance wire to prevent damage to the sig gen. 28 swg nichrome is about 10-11 ohms per metre so that would be fine.

That drawing of the layout is really bad, the wire is clamped but the string is just going to pull the vibration gen towards the bench pulley. The string should go through the stem of the vibration gen to a fixed point.

Yes and it supposed to be an alternate if you don't have the vibration generator.

The diagram is from from AQA A-level Physics Student Guide: Practical Physics

1616767514021.png
 

Nick Mitchener

COMMITTEE
Yes and it supposed to be an alternate if you don't have the vibration generator.

The diagram is from from AQA A-level Physics Student Guide: Practical Physics

View attachment 5857

Ah, sorry. That's why I have not seen it, I was talking about the GCSE spec. We don't do AQA GCE A. Meldes's experiment used to be part of the curriculum long ago.
 
Nick's point about passing the string/wire through the vibration generator and attaching to a fixed point behind is well made. Attaching the load directly to the armature is a good way to ruin a vibration generator. I suspect it's a common mistake.
 
Nick's point about passing the string/wire through the vibration generator and attaching to a fixed point behind is well made. Attaching the load directly to the armature is a good way to ruin a vibration generator. I suspect it's a common mistake.
I put croc-clips onto a piece of 2BA studding, screw that into the vibrator and then clip it onto the wire. Puts zero 'shear' force on the vibrator post.
 
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