"Principle of Electric Motor Rotation" Electric Motors and Generators PPT Courseware 2

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"Principle of Electric Motor Rotation" Electric Motors and Generators PPT Courseware 2

1. Why can the electric motor rotate?

Conjecture: A current-carrying conductor (coil) may experience a force in a magnetic field.

Experimental exploration

①.The effect of magnetic field on energized conductors

Experiments show that when the power is turned on, the conductor rod moves, indicating that the energized conductor receives force in the magnetic field.

Think and explore 2:

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

1. Students, please take a guess? (and give the basis)

2. How to verify your guess?

② Keep the direction of the current unchanged and change the direction of the magnetic field:

The direction of the force is related to the direction of the magnetic field.

③ Keep the direction of the magnetic field unchanged and change the direction of the current:

Conclusion: A current-carrying conductor is affected 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.

Phenomenon analysis:

After the current is energized, the direction of the current passing through the coil is opposite, so the direction of the force is opposite, and the coil rotates in the clockwise direction.

The forces on the upper and lower sides are equal in magnitude, opposite in direction, and act on the same straight line. Therefore, the force on the coil is a balanced force. We call this position the equilibrium position.

Why does the coil stop at equilibrium?

When the coil rotates through the equilibrium position, since the direction of the force on the upper side is upward and the direction of the force on the lower side is downward, the force direction of the coil is opposite to the direction of movement of the coil, so the force on the coil will become a force that hinders the movement of the coil. , at this time, the coil will gradually stop rotating.

Think about it, how can we make the coil continue to rotate?

Change the direction of force on the coil

Change the direction of the magnetic field;

or change the direction of current in a conductor

2. A device that changes the direction of current - commutator

The commutator consists of two metal semicircles that are insulated from each other.

The function of the brush: contacting the half ring to form a closed circuit between the power supply and the coil.

Commutator function:

Whenever the coil just rotates past the equilibrium position, the commutator can automatically change the direction of the current in the coil, and the force direction is always the same, allowing the coil to continue to rotate.

3. Working principle of electric motor

The working principle of an electric motor: The energized conductor is acted upon by a force in the magnetic field to cause the coil to rotate. At the same time, a commutator is used to change the direction of the current in the coil in time to maintain the continuous rotation of the coil.

5. Class summary:

1. Why can the electric motor rotate?

2. The function of commutator:

Whenever the coil just rotates past the equilibrium position, the commutator can automatically change the direction of the current in the coil, and the force direction is always the same, allowing the coil to continue to rotate.

3. The working principle of the electric motor: The energized conductor is acted upon by force in the magnetic field to rotate the coil. At the same time, a commutator is used to change the direction of the current in the coil in time to maintain the continuous rotation of the coil.

Targeted exercises:

1. The direction in which a current-carrying conductor receives a force in a magnetic field is related to the ____ direction and the ____ direction. If the two are in opposite directions at the same time, the direction of the force will be ____. (Fill in “change”, “unchanged” or “not necessarily”)

2. What is the role of the commutator in the DC motor?

3. What measures can be taken to speed up the DC motor?

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Update Time: 2024-11-23

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

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