Paper 4 physics questions ..

[s16]

Hi, I'd really appreciate your help.                                                                                                     1. In half wave rectification .. When you have the voltmeter across the resistor .. If you REVERSE the diode does the graph then become negative ? Or does it just move to the right but still remains positive ?                 2. Flemmings left hand rule .. The second finger points to current, is it normal current or conventional ?              3. When do we use cos and when sin in SHM displacement graphs                                                                   4. If there are two wires next to each other with current going through them but in opposite directions is the flux 0 ? Do they cancel each other out? And is there an overall force between them ? I'm really confused ..                                                                                                                                 5. Ok in a bar magnet the direction of the field is from north to south yes ? So when using right hand grip rule it points to the north ??             Please help !

[s16]

Come on anybody help please :p

[Ykov]

2. Your finger directs from + to -
3. You use cos when the graph does not start at 0, aka a cos graph and you use sin when the graph starts at 0 aka a sin graph
5. Yes, your finger points in the same direction of the magnetic field

[s16]

Ok thank you ok if we have springs won't the graph always start at something below or above 0 ? So shouldn't we always use because for springs ?

[s16]

Hmm .. Could you people at least tell me which board I could ask my questions on and hope for a reply ?

[Twinkle Charms]

Can someone tell me what is the use of backing material in the ultrasound technique?? =S

[s16]

Are you sure you mean ultrasound ? I know it's use in Xrays ..

[A.T]

1:reverse the diode? lol
if u mean capacitor there wont be any change
positive only

4.2 wires current in opposite direction repel each other.


The backing material is pretty much used for damping.

[Twinkle Charms]

oh ok Thanks AT

one more thing, for p4 do we have to go thru AS stuff also? cz if tht is soo its BAD =(

[Onion]

oh ok Thanks AT

one more thing, for p4 do we have to go thru AS stuff also? cz if tht is soo its BAD =(

Not much of AS stuffs though - just the basic knowledge ... something like Alpha particle consists of He atoms, Beta is a beam of electrons, definition of phase difference etc.

[Twinkle Charms]

Are you sure you mean ultrasound ? I know it's use in Xrays ..

its used in both, buh do tell what uses u know in Xrays please.