An ideal long solenoid has turns per unit length and carries steady current . What is the magnitude of the magnetic field inside the solenoid near its center?
Answer and explanation
Correct answer: A.
- Step 1: Applying Ampere's circuital law to a rectangular loop enclosing turns yields .
- Step 2: Cancelling length gives the interior uniform magnetic field: .
Answer
.
Why not the others: is the field at the extreme end edges of the solenoid; doubles the field; and the last expression confuses solenoid geometry with a straight wire.
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