Electromagnetism application: if electron current flows straight into the page (electrons moving away from you), what is the direction of the induced magnetic field lines encircling the conductor?

Difficulty: Easy

Correct Answer: Counterclockwise

Explanation:


Introduction / Context:
Right-hand and left-hand rules help visualize the magnetic field around a current-carrying conductor. A subtlety arises when the problem states “electron current,” because electron flow is opposite to conventional current. This question tests whether you can correctly translate electron flow into an equivalent conventional current direction and then apply the curling rule for magnetic fields.


Given Data / Assumptions:

  • Electron current is specified as moving into the page (away from the observer).
  • Conventional current flows opposite to electron motion.
  • Magnetic field lines around a straight conductor form concentric circles.


Concept / Approach:
First, convert electron flow to conventional current direction: electrons into the page imply conventional current out of the page. Next, apply the right-hand rule for straight conductors: point the right-hand thumb in the direction of conventional current; the curled fingers show the circular magnetic field direction. For current out of the page, fingers curl counterclockwise as viewed by the observer.


Step-by-Step Solution:

Electron flow into page → conventional current out of page. Use right-hand rule: thumb out of page, fingers curl around the wire. Observed field direction on the page: counterclockwise circles.


Verification / Alternative check:
Draw a dot (out of page) to mark conventional current and sketch a few circular arrows around the conductor; standard references show counterclockwise arrows for a current emerging toward the viewer, confirming the result.


Why Other Options Are Wrong:

Clockwise: would correspond to conventional current into the page. Out/Into this page: those describe field direction normal to the page, not the tangential circular direction. None of the above: incorrect because counterclockwise is correct.


Common Pitfalls:
Forgetting that electron flow is opposite conventional current or using the left hand by mistake. Always convert to conventional current first, then apply the right-hand rule.


Final Answer:
Counterclockwise

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