if we double the number of turns of the solenoid keeping the length constant.?

Question

how does the flux get affected?

i am not asking abot B but about flux not flux density.

Answer 1

The magnetic field, B, (or magnetic flux density) at the centre of a solenoid will double.
Doubling the number of turns, n, means that B should double.

Since, B = (μ0 I n)/(2πL)

Also, μ0 = permeability of free space = 4π x 10^-7 N/m^2

[Note: I'm assuming you mean magnetic flux density, B, and not magnetic flux, φ]
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OK then, the magnetic flux should also double since it is proportional to B .

That is, φ=BA

(Assuming area, A, is perpendicular to B)

Answer 2

The flux increases linearly with ampere-turns, but the force increases as the square of the ampere-turns. However, the current is roughly inversely proportional to the number of turns, so the ampere-turns value will stay constant if the solenoid is fed with a fixed voltage. Therefore

under constant voltage, no change in flux

under constant current, 2X the flux

Answer 3

if i remember it alright, the flux is directly proportional to the number of turns. so, if you keep the length constant, and double the number of turns, the flux doubles too.