Electron beam, conventional current, and magnetic field directions

Steps:

• Electron beam direction is opposite to conventional current, as electrons are negative charges.
• From the diagram, electrons travel rightward, so conventional current flows left (←).
• Magnet poles show north above and south below, directing magnetic field downward (↓).
• Combined, current is ← and field is ↓, matching option D.

Why D is correct:

• Conventional current direction opposes electron flow (definition of conventional current as positive charge motion); magnetic field points from north to south pole (right-hand rule for fields).

Why the others are wrong:

• A: Correct current but reverses field direction, ignoring N-to-S convention.
• B: Reverses both current (electron flow) and field (pole orientation).
• C: Correct current but reverses field direction, ignoring N-to-S convention.

Final answer: D