Magnetic field at end of long solenoid (B_end ≈ μ₀nI/2)

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B_end ≈ μ₀nI/2

What each symbol means

SymbolWhat it stands for
ICurrent (A)
nTurns per unit length (m⁻¹)
B_endMagnetic field magnitude near open end of long solenoid (T)

When to use this

Long solenoid: field at open end is approximately half the deep interior value.