CIE A Level Physics復習筆記20.1.3 Fleming's Left-Hand Rule
Fleming's Left-Hand Rule
- The?direction?of the force on a charge moving in a?magnetic field?is determined by the direction of the magnetic field and the current
- Recall that the direction of the current is the direction of?conventional?current flow (positive to negative)
- When the force, magnetic field and current are all mutually perpendicular to each other, the directions of each can be interpreted by?Fleming’s left-hand rule:
- On the left hand, with the thumb pointed upwards, first finger forwards and second finger to the right ie. all three are perpendicular to each other
- The?thumb?points in the direction of?motion?of the rod (or the direction of the force) (F)
- The?first?finger points in the direction of the external?magnetic field?(B)
- The?second?finger points in the direction of conventional?current?flow (I)
Fleming’s left hand rule
Worked Example
State the direction of the current flowing in the wire in the diagram below.
Using Fleming’s left-hand rule:
B = into the page
F = vertically downwards
I = from right to left
Exam Tip
Don’t be afraid to use Fleming’s left-hand rule during an exam. Although, it is best to do it subtly in order not to give the answer away to other students!
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