v
B ⊙ (out)
F = qv×B
+ (High potential)
− (Low potential)
R
I (ext)
Label Table
| Symbol | Meaning | Value/Formula |
|---|---|---|
| B | Magnetic field (out of page) | Given (T) |
| v | Velocity of rod (rightward) | Given |
| l | Length of rod | Given (m) |
| ε | Motional EMF | Bvl (V) |
| F = qv × B | Lorentz force on positive charge | Pushes + charge to top end |
| Current in external circuit | ε/R (A), flows from high to low externally |
Rule: Right-hand rule for F = qv × B with v → right (+x), B → out of page (+z): F = q(v̂ × ẑ) = q(x̂ × ẑ) = −qŷ (downward force in this diagram puts + at top). Always draw and label v, B, l directions before applying the formula.