Read Drift Electrons: Separate Current Direction from Electron Motion
Conventional current and electron drift point in opposite directions. Find drift speed from I = n e A v-d before using the magnetic Lorentz force.
Electricity questions depend on identifying charge, a conducting path and the condition that controls current or magnetic effect.
Magnetic effects have two poles and a direction
Like poles repel · unlike poles attract
Like poles repel and unlike poles attract. Keep the field direction and the material’s magnetic property separate.
Start with the condition
Use the conductor geometry to identify the magnetic field at its surface and preserve the charge sign until the end.
Build the governing relation
The force on one electron is not I L cross B; that expression applies to a complete current-carrying wire segment.
Finish with a physical check
Check the limiting case before selecting an option: remove the special feature in the diagram or make the relevant parameter very large or very small. The result should reduce to a familiar relation.
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- ✓State the physical condition before choosing a formula.
- ✓Keep direction, sign and constraint information explicit.
- ✓Test one limiting case before committing to an option.
Forgetting that electrons are negatively charged reverses the force direction.
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