"Scientific Inquiry: Why Electric Motors Rotate" From Compass to Maglev Train PPT Courseware 2

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"Scientific Inquiry: Why Electric Motors Rotate" From Compass to Maglev Train PPT Courseware 2

electric motor

(1) Main components: ________ and ________.

(2) Principle: The magnetic field has a _________ effect on the energized conductor, and the direction of its effect is related to ________ and ________.

(3) The working process of the motor: When the energized coil has just rotated through the ________ position due to _________, the _________ in the coil is immediately changed so that the force direction of the coil remains the same as the direction of rotation of the coil, so that the energized coil Able to rotate continuously.

Changing the ________ of the motor will change its rotation speed; changing the ________ of the motor will change its direction of rotation.

(4) Energy conversion: The electric motor is the process of converting ________ energy into ________ energy.

1. The effect of magnetic field on current

A current-carrying conductor moves under the action of a force in a magnetic field, and the direction of the force is related to the direction of the magnetic field and the direction of the current. When exploring the relationship between the force direction of a conductor and the direction of current and magnetic field, the method of controlling variables can be used in two steps: (1) Keep the direction of the magnetic field unchanged, change the direction of the current, and observe the direction of force on the wire; (2) Maintain the current Keep the direction unchanged, change the direction of the magnetic field, and observe the direction of force on the wire. When either of these two factors changes, the direction of the force will change; if both factors change at the same time, the direction of the force will not change. Through further experiments, it can be proved that the force of the magnetic field on the current is related to the strength of the magnetic field and the size of the current. The stronger the magnetic field, the greater the current, and the greater the force.

2. Working process of electric motor

The two conductors of the energized coil rotate under the action of two forces in opposite directions in the magnetic field. When the coil rotates to the equilibrium position (the plane of the coil is perpendicular to the magnetic field lines), the two brushes are in contact with the insulating part between the two half rings. , there is no current in the coil, and the coil is not affected by force, but the coil will continue to rotate due to inertia, thus crossing the equilibrium position. At this time, the two brushes and the half ring exchange contact, causing the direction of the current in the coil to change, and the conductor in the coil The direction of the magnetic field force also changes, so it can continue to rotate, so the coil can keep rotating. The element that changes the direction of the current in the coil in the equilibrium position is the contribution of two half rings, and those two half rings are usually called commutators.

Knowledge point 1: The effect of magnetic field on current

1. To change the force direction of a current-carrying conductor in a magnetic field, the following methods are feasible: ()

A.Change the direction of current in an energized conductor

B. Increase the current in the energized conductor

C. Reduce the voltage across the energized conductor

D. Simultaneously change the direction of the current and the direction of the magnetic field in the conductor

2. The picture shown is a globe without an "earth axis" made using electromagnetic levitation technology. The principle is: place a hollow metal ball on an energized coil, and the electromagnetic field generates eddy currents on the surface of the metal ball. The eddy currents interact with the magnetic field to form a magnetic force. This achieves the suspended stillness of the globe. The reason why the globe is suspended in the air is ()

A. Only affected by magnetic force

B.Due to the effect of inertia

C. Not affected by gravity

D. The magnetic force and gravity of the magnetic field balance each other

3. As shown in the figure, support a straight wire AB and place it in the magnetic field of the hoof-shaped magnet. After closing the switch, the straight wire starts to move, which means ____________________; if the positive and negative poles of the power supply are reversed, Let the direction of the current through AB be opposite to the original direction. After closing the switch, the movement direction of wire AB is opposite to the original direction of movement. This also shows that ____.

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"Scientific Inquiry: Why Does the Electric Motor Rotate" From Compass to Maglev Train PPT Courseware 3:

"Scientific Inquiry: Why the Electric Motor Rotates" From Compass to Maglev Train PPT Courseware 3 Review and introduce experimental explanation: There is a magnetic field around the energized wire, which exerts a magnetic force on the magnet. The energized wire can deflect (move) the magnet, indicating that the magnet is affected by magnetic force. .

"Scientific Inquiry: Why Electric Motors Rotate" From Compass to Maglev Train PPT Courseware:

"Scientific Exploration: Why the Electric Motor Rotates" From Compass to Maglev Train PPT Courseware The Effect of Magnetic Field on Current Stretch out your left hand so that your thumb is perpendicular to the other four fingers and in the same plane as your palm. Put your left hand into the magnetic field , let the magnetic field lines be vertical..

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Update Time: 2024-09-06

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