Physics

[leosco1995]

AOA,

How do you draw the magnetic field of the coil in question 6 of this paper? Also, can someone help me with questions 24 and 25 of this paper?

Thanks in advance.

 

[scouserlfc]

there is no other way then the general one drAW the magnetic field like u would for a permanent magnet but also draw in the middle of the coil lines for the magnetic field.
Well i dont remember the MCQs kaisay ho ga

 

[leosco1995]

Okay, got it. Thanks.

Also, I can't believe this thread got buried down in the 2nd page already. Can someone kindly help me on the MCQs?

 

[scouserlfc]

how can 24 be B its almost impossible to it to be B ?? :ugeek:

 

[abcde]

AOA!
For both, the answer is B. For 24, there is one important aspect that you need to consider: even though the coil is connected to an a.c. supply, the current from it would have only one affect on the coil, it would magnetise the coil. This would attract the iron nail by magnetic induction, moving P up. P would continue to be up since the iron nail would always be attracted by the coil no matter the direction of the current in it.
25 depends on facts. Motors and Transformers both use magnetic materials (permanent magnets and soft iron core, respectively). The video tape is also made up of a magnetic material. However, power leads do not consist of any magnetic material (they are usually made of copper, which obviously isn't magnetic!).
Hope this helped.

 

[leosco1995]

I got 25, but I'm still confused about 24. I still don't get why P would move upwards when the iron nail is attracted by the coil..

I also don't understand MCQs 37 and 38 of this paper. Can someone please explain those too?

 

[Silent Hunter]

you dont inderstand which part of 2005 one?

 

[leosco1995]

I forgot to mention it. MCQs 37 and 38.

 

[abcde]

I got 25, but I'm still confused about 24. I still don't get why P would move upwards when the iron nail is attracted by the coil..

I also don't understand MCQs 37 and 38 of this paper. Can someone please explain those too?

Don' you see the pivot at the centre? When one side moves down, the other would obviously move up (recall turning effects of a force).

 

[abcde]

I also don't understand MCQs 37 and 38 of this paper. Can someone please explain those too?

For 37, find out the resistance of the thermistor using the potentiometer equation. Then read off the graph to find the corresponding temperature.
For 38, you can see that the count rate has considerably decreased when a thin card is placed so obviously alpha rays are present. The count rate doesn't deviate much when an aluminium sheet is placed, so beta particles are not emitted but it again falls when lead is placed, indicating that gamma rays are present.

 

[leosco1995]

Alright, I understand them all now. Thanks!

 

[abcde]

You're welcome!