Ampere's Law

Instructions
This simulation shows Ampere's law as it is applied to an ideal solenoid. The solenoid is shown in green as a cross-section, and its magnetic field is shown in red. Adjust the current through the wire with the green slider. Move the blue points to adjust the Amperian loop. The equations below automatically update to show how Ampere's law is applied.
  1. What happens when the loop encloses no current?
  2. What happens when the loop encloses both positive (out of the screen) and negative (into the screen) current?
  3. The four sides of the path contribute different amounts to the total integral. Under which circumstances will the contribution from a side be zero?
  4. The magnetic field within a solenoid is uniform. By playing around with this simulation, can you explain why that must be the case?
– Dave Nero

Information: Ampere's Law