"The Principle of Electric Motor Rotation" Electric Motors and Generators PPT Courseware 4

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"The Principle of Electric Motor Rotation" Electric Motors and Generators PPT Courseware 4

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1. Main components of electric motor: stator with magnets and rotor with coils

2. Simplification of coil:

Coil set A group of coils A coil A length of conductor

3. Conjecture about the rotation of the motor: The rotation of the motor may be related to the magnetic field and coil current. The magnetic field may exert a force on the energized coil and cause the coil to rotate.

In this lesson, we will explore whether the magnetic field has an effect on the current.

Explore the effect of magnetic fields on electric current

Does a current-carrying conductor always move in one direction in a magnetic field? If not, what factors are it related to?

① A current-carrying conductor is acted upon by a force in a magnetic field. Is the direction of the force related to the direction of the current?

② A current-carrying conductor is acted upon by a force in a magnetic field. Is the direction of the force related to the direction of the magnetic field?

Experiments show:

A current-carrying conductor will be acted upon by a force in a magnetic field, and the direction of the force is related to both the direction of the current and the direction of the magnetic field.

Effect of magnetic field on energized coil

At the beginning, the plane of the coil is parallel to the magnetic induction lines. After energization, the current directions on the red side and the blue side are different, and the direction of the force is opposite, and the coil rotates; when the coil turns to the red side facing up and the blue side facing down, The forces on the red side and the blue side are equal in magnitude and opposite in direction, and are on the same straight line. Due to inertia, the coil will swing back and forth several times, but will eventually stop at this position. (i.e. equilibrium position)

Since the energized coil will stop when the magnetic field rotates to the equilibrium position, how can we make the energized coil continue to rotate in the magnetic field?

How electric motors work

The electric motor is made based on the basic principle that an energized coil is forced to rotate in a magnetic field.

A motor powered by a DC power source is called a DC motor.

Basic structure of DC motor

A and B are brushes

Function: Contact with the half ring to form a closed circuit between the power supply and the coil.

E and F are commutators (two semicircular copper rings):

Function: Change the direction of the current in the coil in time so that the force direction is always the same and the coil keeps rotating.

Class summary

Explore the rotation principle of electric motors

1. The effect of magnetic field on current

A current-carrying conductor is acted upon by a force in a magnetic field, and the direction of the force is related to the direction of the current and the direction of the magnetic field.

2. The function of commutator

When the coil rotates past the equilibrium position, the direction of the current in the coil is automatically changed.

3. Working principle of electric motor:

The energized coil is forced to rotate in the magnetic field.

4. Energy conversion when the motor is working

Electrical energy is converted into mechanical energy.

Class exercises

1. When the coil rotates through the equilibrium position, the current passing through the coil is 0, but the coil can still rotate. The reason is ()

A. Due to the gravity of the coil B. The coil has inertia

C. Due to the action of the commutator D. Due to the action of the magnetic field force

2. For a fully assembled DC motor model, the coil does not rotate after the power is turned on. After the rotor is moved by hand, the coil starts to rotate normally. The reason why the motor model does not rotate at first may be ()

A. The coil is exactly in the balanced position B. The brush and the commutator are in poor contact

C. The magnet is magnetic or the current in the coil is not large enough. D. There is an open circuit in the coil.

3. Electric motors are widely used in many household appliances. Please list the names of three household appliances equipped with electric motors________; __________; _______.

4. In order to explore the effect of the magnetic field on the current, use the figure to conduct experiments. When the circuit is closed, the current-carrying conductor bar AB will be forced to _______. If the magnet is removed, the current-carrying conductor bar AB will ___________; if In the experiment shown in the figure, if the direction of the current in the conductor AB is changed, the direction of movement of the energized conductor bar AB will be______; if the direction of the current is kept unchanged in the experiment and the positions of the two poles of the magnet are exchanged, the direction of the force on the energized conductor bar AB will be_ _____; Therefore, experiments show that: A current-carrying conductor is acted upon by a force in a magnetic field, and the direction of the force is related to __________ and ___________.

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Update Time: 2024-10-02

This template belongs to Physics courseware Guangdong and Shanghai Edition Ninth Grade Physics Volume 2 industry PPT template

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