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Homework Help: Betatron, derivation of expressions

  1. Oct 22, 2012 #1
    Hi!

    I've got a problem with question 5 on this paper:

    http://www.freeexampapers.com/past_papers.php?l=Past_Papers%2FAEA%2FPhysics%2F2006/

    Download AEA-PHYS-PP-MayJune-2006-AEA-Paper-1342.pdf.

    Starting from b) i), we got that:

    ε=Δ∅/Δt → W=εe

    Where W is denotes work, ε is e.m.f

    Also, for ii) work can be written as:

    W=2∏rF

    in iv) we use F=Δp/Δt=2erΔB/Δt

    as during one cycle mementum changes its direction to the opposite twice. From all that we got:

    Δ∅=4∏r^2ΔB

    Where 4 comes from? It should be deltaB times area of loop. I tried to check it if 2s does not cancel each other but they don't, where's the mistake?
     
  2. jcsd
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