A horizontal wire carries a conventional current from west to east. The wire is placed in a uniform magnetic field directed vertically downwards. In which d...
Question 1 Report
A horizontal wire carries a conventional current from west to east. The wire is placed in a uniform magnetic field directed vertically downwards.
In which direction is the force on the wire?
Answer Details
The direction of the force on a current-carrying conductor in a magnetic field is found using Fleming's left-hand rule. Point the first finger in the direction of the magnetic field, the second finger in the direction of the conventional current, and the thumb then points in the direction of the force.
Here the magnetic field is directed vertically downwards and the conventional current flows from west to east. Aligning the first finger downwards (field) and the second finger pointing east (current), the thumb points north. The force on the wire is therefore directed northwards.
A useful way to practise this: hold your left hand so the first finger can point down while the second finger extends towards the right (east). Your thumb will naturally extend forwards (north). Getting comfortable with this hand orientation for non-standard field directions is essential for examination questions where the field and current are not in the usual textbook arrangement.
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