electromagnetic force or Lorentz force production.

*Lorentz force states that "when a current carrying conductor is*

placed in a magnetic field, it is subject to a force which we call

Lorentz force ".

placed in a magnetic field, it is subject to a force which we call

Lorentz force ".

The magnitude of the force depends upon the orientation of the

conductor with respect to the direction of the field. The force is

greatest when the conductor is perpendicular to the field and zero

when it is parallel to it. Between these two extremes, the force has

intermediate values.

The maximum force acting on a straight conductor is given by

F = Bli

Where F : Is the force acting on the conductor (N),

B : Is the flux density of the field (T), and,

l : Is the length of the conductor facing the magnetic field(m).

i: the current in the conductor (A).

The direction of the magnetic force can be determined by using

Felming left hand rule. Before going to show this rule, it is better to

explain the physical meaning of the lorentz force. This can be easly

explaind by with the help of the following two figures (Fig. And

Fig. ). For a current flowing into the page of this book, the circular

lines of force have the direction shown in Figure 2.32a. The same

figure shows the magnetic field created between the N, S poles of a

powerful permanent magnet.

The magnetic field does not, of course, have the shape shown in

the figure because lines of force never cross each other. What,

then, is the shape of the resulting field?. To answer the question,

we observe that the lines of force created respectively by the

conductor and the permanent magnet act in the same direction

above the conductor and in opposite directions below it.

Consequently, the number of lines above the conductor must be

greater than the number below. The resulting magnetic field

therefore has the shape given in Figure 2.32b.

Recalling that lines of flux act like stretched elastic bands, it is

easy to visualize that a force acts upon the conductor, tending to

push it downward.

Now let us Define Felmeng left hand rule It is illustrated in Fig.

6-9.

6-9.

The direction of the force can also be determined by using the

right-hand screw rule, illustrated in Fig.2.2(b).

Turn the current vector i toward the flux vector B. If a screw is

turned in the same way, the direction in which the screw will move

represents the direction of the force f.

Note that in both cases (i.e., determining the polarity of the

induced voltage and determining the direction of the force) the

moving quantities (v and i ) are turned toward B to obtain the

screw movement.

Equations (2.1) and (2.2) can be used to determine the induced

voltage and the electromagnetic force or torque in an electric

machine. There are, of course, other methods by which these

quantities (e and f) can be determined.

http://faculty.ksu.edu.sa/eltamaly/Documents/Courses/EE%20339/

For the current-carrying conductor shown in Fig.3.3(a), the

force (known as Lorentz force) produced on the conductor can be

determined from the following equation:

f = Bli (3.2)

where B, l, and i are mutually perpendicular. The direction of

the force can be determined by using the Fleming’s Left Hand Rule

or right-hand screw rule as explaind in the previous chapter and

are stated in the following. The direction of the force is illustrated

in Fig.3.3(b).

Equations (3.1) and (3.2) can be used to determine the induced

voltage and the electromagnetic force or torque in an electric

machine. There are, of course, other methods by which these

quantities (e and f) can be determined.

right-hand screw rule, illustrated in Fig.2.2(b).

Turn the current vector i toward the flux vector B. If a screw is

turned in the same way, the direction in which the screw will move

represents the direction of the force f.

Note that in both cases (i.e., determining the polarity of the

induced voltage and determining the direction of the force) the

moving quantities (v and i ) are turned toward B to obtain the

screw movement.

Equations (2.1) and (2.2) can be used to determine the induced

voltage and the electromagnetic force or torque in an electric

machine. There are, of course, other methods by which these

quantities (e and f) can be determined.

**Source ( pdf )**

http://faculty.ksu.edu.sa/eltamaly/Documents/Courses/EE%20339/

MAGNETIC%20CIRCUITS.pdf

**Electromagnetic Force, f**For the current-carrying conductor shown in Fig.3.3(a), the

force (known as Lorentz force) produced on the conductor can be

determined from the following equation:

f = Bli (3.2)

where B, l, and i are mutually perpendicular. The direction of

the force can be determined by using the Fleming’s Left Hand Rule

or right-hand screw rule as explaind in the previous chapter and

are stated in the following. The direction of the force is illustrated

in Fig.3.3(b).

*Fleming’s Left Hand Rule:*

“Hold out your left hand with forefinger, second finger and thumb

at right angles to one another. If the forefinger represents the

direction of the field, and the second finger that of the current, then

thumb gives the direction of the motion or force.”

“Hold out your left hand with forefinger, second finger and thumb

at right angles to one another. If the forefinger represents the

direction of the field, and the second finger that of the current, then

thumb gives the direction of the motion or force.”

*Right-Hand Screw Rule:*

Turn the current vector i toward the flux vector B. If a screw is

turned in the same way, the direction in which the screw will move

represents the direction of the force f.

Note that in both cases (i.e., determining the polarity of the

induced voltage and determining the direction of the force) the

moving quantities (v and i ) are turned toward B to obtain the

screw movement.

Turn the current vector i toward the flux vector B. If a screw is

turned in the same way, the direction in which the screw will move

represents the direction of the force f.

Note that in both cases (i.e., determining the polarity of the

induced voltage and determining the direction of the force) the

moving quantities (v and i ) are turned toward B to obtain the

screw movement.

Equations (3.1) and (3.2) can be used to determine the induced

voltage and the electromagnetic force or torque in an electric

machine. There are, of course, other methods by which these

quantities (e and f) can be determined.