IGCSE physics easy question

[holtadit]

Look at question 9 (c) of the attached paper.

How do they get I^2 R and what formula are they referring to. ?

[holtadit]

HELP!

[holtadit]

Also question 9 c ii of the attached paper .

THIS A DIFFERENT QUESTION FROM THE ONE ABOVE

How do u know in which way the flexible wire moves ? I applied flemings left hand rule but i dont know in which way the index finger points... where is the North and South poles ?

[astarmathsandphysics]

Half am hour

[holtadit]

finally someone decides to help 

[astarmathsandphysics]

The attacjed file is corrupt. I looked up the question on my version of the paper and it doesnt look the same as yours.

[holtadit]

For my first question see paper 3 may june 2008

for the second question see paper 3 november 2008

[astarmathsandphysics]

P=IV but Y=IR so P=I(IR)=I^2R

[astarmathsandphysics]

Use the right hand grip tule on the thick wire to find the direction of the field - clockwise and left hand rule on thin wire to find direction of force - towards thick wire. Alternativley you could just use - like currents attract.

[holtadit]

for the left hand rule where would the index finger (magnetic field) point ? and why ?

[Ghost Of Highbury]

lemme explain it to u ..hold on

[Ghost Of Highbury]

i know the diagram sucks, but try to understand plz..

the middle finger shud point downwards, and the index finger shud point straight...hope u get it.

if not tell me..

[astarmathsandphysics]

Wxactly right