what happens to the force (magnitude and direction) on the wire when
(i) the size of the current through the wire is increased ?
(ii)
A weaker magnet is used ?
(iii) the size of the current the same but the direction of the current is reversed
Force on a wire = i B x L
where i = current magnitude
B = magnetic field vector
L = wire length and direction vector
x denotes vector cross product
(i) force doubles and direction remains the same
(ii) less force, same direction
(iii) same force, opposite direction
To understand what happens to the force on a wire when different factors change, we need to consider the interaction between the current-carrying wire and a nearby magnet. The force experienced by the wire is described by the right-hand rule of electromagnetism, also known as the "left-hand rule for motors" or "Fleming's left-hand rule".
(i) When the size of the current through the wire is increased:
The magnitude of the force on the wire is directly proportional to the current running through it. According to Fleming's left-hand rule, if you point your thumb in the direction of the conventional current (opposite to electron flow), with your fingers pointing in the direction of the magnetic field lines created by the magnet, the force experienced by the wire will be in the direction that your palm faces. Therefore, increasing the current increases the magnitude of the force on the wire.
(ii) When a weaker magnet is used:
The magnitude of the force on the wire is directly proportional to the strength of the magnetic field. If a weaker magnet is used, the magnetic field lines generated by the magnet will be weaker. Consequently, the force experienced by the wire will be reduced.
(iii) When the size of the current remains the same but the direction of the current is reversed:
When the size of the current in the wire remains the same but the direction changes, the force on the wire will be reversed. According to Fleming's left-hand rule, if you reverse the direction of the current (by reversing the direction of your thumb), the force experienced by the wire will also reverse its direction. The magnitude of the force will remain the same as long as the current remains constant.
In summary,
- Increasing the size of the current through the wire increases the magnitude of the force on the wire.
- Using a weaker magnet reduces the magnitude of the force on the wire.
- Reversing the direction of the current in the wire reverses the direction of the force on the wire.