# Flux and solenoid [closed]

Find the flux through one end of semi infinite solenoid ( assume necessary parameters )

My method Consider that there is an imaginary other half as well with both clockwise and anticlockwise currents . Consider flux as $$F$$ through face . So we can say$$F = unIA -F$$.is my way of approaching the flux magnitude is correct ?

## closed as off-topic by Aaron Stevens, Jon Custer, John Rennie, ZeroTheHero, Kyle KanosNov 12 at 12:17

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Yes (and you have a nice method there, as long as you present it correctly).

• I would say that if an answer to a posted question can just be "yes, you are correct", then it is mostly like an off-topic question as falling under a sort of "check my work" mentality. – Aaron Stevens Nov 8 at 23:19

In a flux producing solenoid, the current floes in only one direction at a time. With an infinitely long solenoid F = uniA should work. Take away the imaginary half and your left with F = (1/2)uniA at the open end. (The missing half has diverged through the coils before reaching the end.)

• I downvoted because there is no physical reasoning here. – Andrew Steane Nov 8 at 18:33
• The logic is straight forward. If you remove half the coil which is producing the flux, you lose half the flux (at the break point). – R.W. Bird Nov 9 at 19:39
• Yes, the answer is true, but we need some reasoning to show why it is true. In this case the reasoning is based on the superposition principle which applies here because fields are produced by sources and the equations are linear. But if the equations were non-linear this reasoning would fail. – Andrew Steane Nov 9 at 22:40