A long solenoid that has 1 125 turns uniformly distributed over a length of 0.405 m produces a magnetic field of magnitude 1.00 × 10⁻⁴ T at its center. What current is required in the windings for that to occur?
Part 1 of 3 - Conceptualize
We estimate the current in the windings to be on the order of one ampere. The field is larger than that typically produced by a single wire because of the many turns, not because the current is very large.
Part 2 of 3 - Categorize
We will use the equation for the magnitude of the magnetic field at the center of a solenoid to determine the current.
Part 3 of 3 - Analyze
The magnetic field at the center of a solenoid of length ℓ with N turns carrying current I is given by
B = μ₀(N/ℓ)I,
so solving for the current and substituting the given values, we have
I = Bℓ / μ₀N
= (( × 10⁻⁴ T)( m)) / ((4π × 10⁻‑⁷ T · m/A)( )) = mA.