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Author Topic: ALL PHYSICS DOUBTS - POST HERE !!  (Read 230767 times)

Offline Ivo

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #1425 on: May 25, 2010, 06:43:02 pm »
Quote from: ~VIN1094~ on May 25, 2010, 06:41:43 pm
i didnt get u ?!? ??? :-[

I'm just saying the potential difference between cathode and anode is 600V d.c.
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Offline 8T

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #1426 on: May 25, 2010, 06:43:15 pm »
Ivo, uR the best :P
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Offline Ivo

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #1427 on: May 25, 2010, 06:44:26 pm »
Quote from: A@di on May 25, 2010, 06:40:45 pm
Its just cooler than the hot cathode

H = Heat.

By the way, is heat of cathode to aid the thermionic emission?
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Offline Ivo

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #1428 on: May 25, 2010, 06:44:44 pm »
Quote from: 8T on May 25, 2010, 06:43:15 pm
Ivo, uR the best :P

Thank you!  8)
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Offline Vin

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #1429 on: May 25, 2010, 06:44:56 pm »
Quote from: A@di on May 25, 2010, 06:38:13 pm
Yea heat loss is due to current. H = I^2r...(I^2)!!!

yes, its A, thicker.

same as P = I2R

where P is the power loss due to heat ..
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Offline Ghost Of Highbury

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #1430 on: May 25, 2010, 06:45:07 pm »
Quote from: Ivo on May 25, 2010, 06:44:26 pm
By the way, is heat of cathode to aid the thermionic emission?

Yes
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Offline Ivo

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #1431 on: May 25, 2010, 06:46:17 pm »
Quote from: ~VIN1094~ on May 25, 2010, 06:44:56 pm
same as P = I2R

where P is the power loss due to heat ..

The reason behind P=(I^2)R:

Combine P=IV and V=IR then you get the above equation!
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Offline Vin

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #1432 on: May 25, 2010, 06:47:08 pm »
Quote from: Ivo on May 25, 2010, 06:43:02 pm
I'm just saying the potential difference between cathode and anode is 600V d.c.

FYI, :P because in the question its 600 V .. rest of the world uses 10,000 to 60,000 V for CROs ;)
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Offline soraam

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #1433 on: May 25, 2010, 06:49:54 pm »
http://www.freeexampapers.com/FreeExamPapers.com_.php?__lo=SUdDU0UvUGh5c2ljcy9DSUUvMjAwNiBKdW4vMDYyNV9zMDZfcXBfMS5wZGY=


question 37

i know why its positive but the second part is kinda unreasonable

the answer is C  ...
but why??
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Offline Fastal

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #1434 on: May 25, 2010, 06:52:20 pm »
only the cathode gets red hot. the anode just focuses the electrons onto the flourescent screen. its relatively cool to the cathode
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Offline soraam

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #1435 on: May 25, 2010, 06:53:15 pm »
why
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Offline Shazizzzle

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #1436 on: May 25, 2010, 06:55:46 pm »
Quote from: soraam on May 25, 2010, 06:53:15 pm
why


What do you mean, 'why'?
In a CRO, it is the CATHODE that is heated, and thus on heating, releases electron beams by thermionic emission.
The anode is just connected to the + power supply to ACCELERATE the electrons.
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Offline soraam

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #1437 on: May 25, 2010, 06:57:15 pm »
oh sh*t
thank you i totaly forgot hoe the CRO is made
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Offline the_grim_reaper

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #1438 on: May 25, 2010, 06:59:46 pm »
Quote from: A@di on May 25, 2010, 06:37:21 pm
AC - The direction of current periodically reverses , positive to negative, negative to positive, positive to negative...and so on

DC  - is the unidirectional flow of electric charge

hahaha you see that's the problem :D. What exactly do you mean by direction??? A current in a wire will flow through the wire right?? It won't exactly change direction and move west or east?? LOL :D.

Quote from: Ivo on May 25, 2010, 06:36:43 pm
I think this is it:

AC: alternating current (switches from positive to negative terminal and back to postivie)

DC: direct current (only flows from postivve to negative)

Also, please can someone answer my last post, thanks!

So what i can get from your answer is that  say 1 terminal is positive then it becomes negative then again positive and so on... But there's just one problem. Won't it just move backwards and forwards (the current)?? Like one step ahead then 1 step back?? LOL :D.

(Please really sorry to disturb all of you guys but I've never understood this (from Grade 6) and I believe if I don't clear this doubt now, it'll haunt me for the rest of my life)...
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Offline the_grim_reaper

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #1439 on: May 25, 2010, 07:02:01 pm »
Quote from: Shazizzzle on May 25, 2010, 06:55:46 pm
What do you mean, 'why'?
In a CRO, it is the CATHODE that is heated, and thus on heating, releases electron beams by thermionic emission.
The anode is just connected to the + power supply to ACCELERATE the electrons.

"What do you mean, 'why'?" hahahaah cracked me up. Just relax Shaz!!! :D.
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