28th October 2003, 02:06 AM
I also no A levels! WAKAKAKA!!! Maybe the smarter ones should be commenting here instead....... hehe
Originally Posted by Clown
28th October 2003, 11:13 AM
paramagnetism is not taught in A's... at least not for my time.
Originally Posted by NiVleK
28th October 2003, 11:30 AM
28th October 2003, 12:27 PM
The Second question is vague as it does not spell out the experiment. I can only think of two possible aim of this setup.....
1- Comparing if the soft iron core or the aluminium ring is magnetised ???
2- To see if the aluminium ring will lavitate....??? Was there some flux pattern drawing required for this paper???
Before you start thinking of what happens to the aluminium ring....you have to look at the electrical characteristics (electrical conductivity) of aluminium.
Aluminium's electric conductivity is second only to copper. It will not be magnetized.
Electric capacitance per unit dimensions is large. Due to these favorable characteristics, it is widely applied in capacitors, (paper capacitor, etc.) loud speaker parts, electric cable wrapping and other electric appliances. Also used in basic shielding for EMI EMC problems....
28th October 2003, 02:39 PM
You're not alone.......
Originally Posted by aosis
28th October 2003, 03:38 PM
I think for qn 1, u need not know the refractive index(they vary)... the critical part is that for plastic, total internal reflection has not taken place. as for glass, total internal reflection has taken place and thus ans = A
Originally Posted by innovas1
As for 2, since the diagram quite vague, here is my take.
When the switch is on, a magnetic field is set up in the solenoid. A current will be set up in the aluminum ring (non-magnetic) and flows in such manner to oppose the increase in flux linkage (Lenz's Law). Since it is an AC, the magnetic field in the solenoid is an alternating one. Thus, the current flowing in the ring is an alternating one as well. Hence, the ring will be suspended. (When the solenoid facing the Al ring is a north/south pole, the Al ring facing the solenoid will be a north/south pole as well.)
Assuming the area of the ring not changed. Thinner implies more resistance in the ring (current induced in ring decreases) and the ring is lighter. cannot conclude. but if u ignore the effect of resistance, with a lighter ring, the ring will levitate at a higher height.
If DC, no constant change in magnetic flux linkage. Hence, the ring will 'jump' momentarily up, after which it will drop back down and remain at the down position... when off, the same thing happen...
my 2 cents worth
Last edited by bearycute; 28th October 2003 at 03:45 PM.
29th October 2003, 12:30 AM
isn't silver no.1 in electrical conductivity?
Originally Posted by sulhan
29th October 2003, 12:54 AM
side track....the conductivity .....
Here is the conductivity of the metals in comparison...
Metal Conductivity - Electrical conductivity.
The values are a measure of how much current will flow in a standard sample when it is attached to 1 volt.
1 silver 670
2 copper 640
3 aluminium 410
4 mild steel 70
To answer your question..Yes....no doubt that Silver has the highest...
29th October 2003, 12:58 AM
for question 1 i can only think of birefringence. but dunno if O level got teach of this. Birefringence occurs when the light source is seperated in 2 different rays, Odinary and Etraordinary rays.
29th October 2003, 01:10 AM
29th October 2003, 01:15 AM
29th October 2003, 03:20 AM
29th October 2003, 03:43 AM