Motors and Generators - Physics
1. Motors use the effect of forces on current-carrying conductors in magnetic fields
Discuss the effect on the magnitude of the force on a current-carrying conductor of variations in:
The strength of the magnetic field in which it is located
• The magnitude of the force is proportional to the magnetic field strength. Thus, an increase in magnetic field strength will cause an increase in the force on the wire and a decrease in magnetic field strength will cause a decrease in force on the wire.
The magnitude of the current in the conductor
• The magnitude of the force is also proportional to the current (I). Thus, an increase in current will result in an increase in force whilst a decrease in current will lead to a decrease in force.
The length of the conductor in the external magnetic field
• The magnitude of the force is also proportional to the length (L).Thus, an increase in the length of the wire within the field will result in an increase in force on the wire, whilst a decrease in the length of the wire in the magnetic field will lead to a decrease in force.
The angle between the direction of the external magnetic field and the direction of the length of the conductor.
• The force is at its maximum when the current carrying conductor is at right angles to the field (sin90=1), and is zero when the conductor is parallel to the field (sin0=0). The magnitude of the force is proportional to the components of the magnetic field that is at right angles to the current carrying conductor (sin90 =1).
The above points can be mathematically expressed as:
F = nBILsin(0)
Where: F= magnitude of the force (N)
N = number of turns of wire B= magnetic field strength (T) I= current (amps)
L = current length (m)
Sinθ= angle between the magnetic field and current.
Describe qualitatively and quantitatively the force between long parallel current-carrying conductors : F/l =kll/d
• The force (F) per unit length (l) between two
Discuss the effect on the magnitude of the force on a current-carrying conductor of variations in:
The strength of the magnetic field in which it is located
• The magnitude of the force is proportional to the magnetic field strength. Thus, an increase in magnetic field strength will cause an increase in the force on the wire and a decrease in magnetic field strength will cause a decrease in force on the wire.
The magnitude of the current in the conductor
• The magnitude of the force is also proportional to the current (I). Thus, an increase in current will result in an increase in force whilst a decrease in current will lead to a decrease in force.
The length of the conductor in the external magnetic field
• The magnitude of the force is also proportional to the length (L).Thus, an increase in the length of the wire within the field will result in an increase in force on the wire, whilst a decrease in the length of the wire in the magnetic field will lead to a decrease in force.
The angle between the direction of the external magnetic field and the direction of the length of the conductor.
• The force is at its maximum when the current carrying conductor is at right angles to the field (sin90=1), and is zero when the conductor is parallel to the field (sin0=0). The magnitude of the force is proportional to the components of the magnetic field that is at right angles to the current carrying conductor (sin90 =1).
The above points can be mathematically expressed as:
F = nBILsin(0)
Where: F= magnitude of the force (N)
N = number of turns of wire B= magnetic field strength (T) I= current (amps)
L = current length (m)
Sinθ= angle between the magnetic field and current.
Describe qualitatively and quantitatively the force between long parallel current-carrying conductors : F/l =kll/d
• The force (F) per unit length (l) between two