"Electromagnet" Electromagnetic Phenomenon PPT Courseware 2

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"Electromagnet" Electromagnetic Phenomenon PPT Courseware 2

1. Electromagnet

1. The essence of an electromagnet: a energized solenoid with an iron core.

2. The reason why the magnetism of electromagnet is stronger than that of solenoid is:

The magnetic field after the iron core is magnetized is mixed with the magnetic field of the solenoid, which strengthens the magnetism.

2. Magnetic properties of electromagnets

Question: What factors are related to the magnetic size of electromagnets?

Guess the strength of the magnet may be related to the size of the current, the number of turns and the shape of the coil.

For solenoids with the same appearance, what is the relationship between the magnetic strength of the electromagnet and the number of turns of the coil?

How to judge the strength of magnetism:

The magnetic strength of the solenoid can be judged by the number of small iron nails it attracts. This method is called __________

(1) Change the current in the circuit;

(2) Replace the solenoid with a different number of turns.

3. Application of electromagnets

In life, we often see some large machines at work (such as large cranes), and their current can reach tens of amps or hundreds of amps. It is very dangerous to control or operate directly. So how can we control these powerful currents? ?

Knowledge points of this lesson

1. The essence of electromagnet:_______________

2. Advantages of electromagnets: ______________

3. The magnetic strength of electromagnets is related to _______, ________, and _______

4. The polarity of the electromagnet is related to _______ and ________

5. The reason why the magnetism of electromagnets is stronger than that of solenoids is ____________________

4. Electromagnetic relay

1. The structure of electromagnetic relay

2. The essence of electromagnetic relay

It is a switch controlled by an electromagnet.

practice

1. The picture is a schematic diagram of an automatic water level alarm. Try to explain how it works.

2. The picture is a schematic diagram of an automatic temperature alarm. To make a mercury thermometer, a piece of metal wire is sealed in a glass tube. When the temperature reaches the temperature indicated by the lower end of the metal wire, the bell will sound and an alarm signal will be sent. Explain how it works.

3. The picture shows the schematic diagram of a DC bell. B is the armature and A is the elastic piece. Try to explain how it works.

Advantages of electromagnets

1. Low voltage and weak current can be used to control high voltage and strong current.

2. Remote operation and automatic control can be achieved

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Update Time: 2024-11-22

This template belongs to Physics courseware Lu Jiao Edition Ninth Grade Physics Volume 2 industry PPT template

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