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Magnetism

Blazing goIITian

Joined:	5 Dec 2007
Post:	704

9 Jan 2008 22:51:09 IST

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300

electromagnetism

None

a small circular coil of radius r n no.of turns n is placed at d centre of anoder big circular coil of radius R n no.of turns N. initially d 2 coils r coplanar n d same current i flows thru both coils den d amount of work done in rotating d small coil about any of its diameter by an angle pie vil b ?

3 long wires of resistances in d ratio 3:4:5 r connected in parallel 2 each oder as shown if net force on middl wire is 0 den d1/d2 = ?

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Pratyush Pande

Cool goIITian

Joined: 2 Jan 2008

Posts: 58

11 Jan 2008 09:09:08 IST

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B at the centre of the bigger ring =

₀Ni/2R

magnetic moment of the smaller one = ni

r²

potential enrgy of a dipole in B = - MBcos

the work done wil be change in PE = MB(cos 0 - cos

)

= 2MB

₀

Nnr²i²/R

see if V is the potenial across them the currents will be V/3 , V/4 , V/5

the force on the middle wiure wil b 0 if the forces of the other two balace each other

dF/dl =

₀i₁i₂/2

nwo the 2 force r equal

₀i₁i₂/2

d₁=

₀i₃i₂/2

d₂

hence d₁/d₂ = i₁/i₃

= V/3 / V/5

= 5/3

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