DC MOTOR PRINCIPLEMagnetic Force

MOTOR PRINCIPLE When a straight wire carrying a current is

placed in an external magnetic field, the interaction of the circular magnetic field produced by the current and the external magnetic field produces a magnetic force that acts on the wire.

MOTOR PRINCIPLENote: that the magnetic force is represented by

the symbol Fm .

The action of the magnetic force on a conductor is known as the motor principle, which states that

When a current-carrying conductor is in an external magnetic field, but is not parallel to the field, it experiences a magnetic force.

MAGNETIC FORCE

MAGNETIC FORCE The magnetic force involved in the motor principle

depends on three factors:

1. Amount of current through the wire as the current increases, the magnetic force increases

2. Magnitude of the external magnetic field as the strength of the external magnetic field increases, the

magnetic force increases

3. Length of the conducting wire that is perpendicular to the magnetic field as the perpendicular component of the wire’s length

increases, the magnetic force increases

MAGNETIC FORCE

MAGNETIC FORCEAn 8.50-cm length of conducting wire lies perpendicular to an external magnetic field of magnitude 4.20 mT [right] as shown in Figure 12.25.The SI prefix milli- (m) is equal to 103. If there is a current of 2.10 A in the conductor, calculate the magnitude and determine the direction of the magnetic force on the wire.

FORCE BETWEEN TWO WIRES

FORCE BETWEEN TWO WIRES

MAGNETIC FORCEAmpère placed two 1.50-m wires parallel to each other so that they were 4.80 cm apart. He delivered a current of 6.50 A to the wires. Both wires experienced an external magnetic field of 2.71x10-5 T. Determine the force on one of the wires.