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# A2 Design Experiment question.. HELP!! watch

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1. The question is this:

"Design an experiment to measure the mass per unit length n of a length of copper wire. The wire will be placed in an external uniform magnetic field and I will have a variable power supply"

Equipment:

- set of slotted masses
- bare copper wire
- AC ammeter
- variable AC power supply
- uniform magnetic field setup
- other equipment normally available in a lab...

Sections:

- Method
- Observations (what are you going to measure?)
- Analysis (how are you going to use what you measure?)
- Any other good points

Before this, we had to find an expression for the speed of a stationary wave in terms of n (mass per unit length) and T (the tension in the wire) which came out to be:

c= squared root of (T/n)

we then considered a conductor (with current I) in an external magnetic field... F= BIL ... if the current is alternating in the wire, the force would alternate upwards and forwards.

If the wire is fixed at both ends, a stationary wave is formed. Hence we can measure the wavelength for the stationary wave.

ANYONE CAN GIVE ME SOME HELP?? THANK YOU!!!
2. Adjust length so get a standing wave with Annitmode in middle and nodes at each end.

c = f x lambda.

f is 50 Hz if using mains based PSU. Resonance. Driving freq = natural freq of wire.

lambda / 2 = distance between 2 nodes on a standing wave.

Should be enough there to work out n.
3. This would be a fine xperiment for our designing paper 2mrw;D

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Updated: October 18, 2006
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