Physics knowledge in the third year of junior high school, what are the physics knowledge points in

The phenomenon of inducing electromotive force due to changes in magnetic flux (when a part of a conductor in a closed circuit moves to cut magnetic field lines in a magnetic field, an electric current is generated in the conductor, and this phenomenon is called electromagnetic induction.) ）

The conditions under which the induced current is generated.

1.The circuit is closed and on.

2.The magnetic flux passing through a closed circuit changes.

If a condition is missing, no induced current will be generated).

Types of induced electromotive force: kinetic electromotive force and induced electromotive force.

The kinetic electromotive force is the induced electromotive force generated by the conductor's own cutting magnetic inductance line movement in the magnetic field, and its direction is judged by the right-hand rule, so that the thumb is perpendicular to the remaining four fingers and are in a plane with the palm, put the right hand into the magnetic field, let the magnetic inductance line perpendicularly penetrate the palm, the thumb points to the direction of the conductor's movement, and the remaining four fingers point to the direction of the dynamic electromotive force. The direction of the generated electromotive force is the same as that of the induced current generated. The direction of the kinetic electromotive force determined by the right-hand rule conforms to the law of energy conversion and conservation.

Induced electromotive force is caused by a change in the strength of the magnetic field passing through the closed coil to produce a vortex electric field, resulting in the directional motion of the electric current. Its direction conforms to Lenz's law. The thumb of the right hand points in the opposite direction of the change in the magnetic field, and the four fingers are clenched into a fist, and the direction of the four fingers is the direction of the induced electromotive force.

The basic property of a magnetic field is the effect of a magnetic force on the magnet placed in it.

When the current is the same, the electromagnet is inserted into the core.

The third year of junior high school physics knowledge points:Molecular thermal exercise is often examined.

1. Diffusion phenomenon:

Solids, liquids, and gases can all diffuse phenomena, but the speed of diffusion is different, the diffusion speed between gases is the fastest, and the diffusion speed between solids is the slowest. The diffusion speed is related to the temperature, the higher the temperature, the more intense the irregular movement of the molecules, and the faster the diffusion.

2. Intermolecular forces:

The gravitational and repulsive forces of intermolecular interactions exist simultaneously. (Different situations manifest themselves as different forces).

The best way to learn physics in junior high school:The world of junior high school physics is real and rich. Imagine what a world without sound would be?

The Silent World fantasy article is out right away. The city is modernizing, the buildings with glass walls are getting higher and higher, the night is getting brighter and brighter, and the dazzling light brings a lot of inconvenience to the residents' lives, so think about "how to reduce light pollution".

This is not something that can be solved in one sentence or two, so it is recommended to read the book. You try, People's Education Publishing House, enter the official website, there is a subject direct below, click physics, and then click on the grade book under the teacher center to browse, you can see the table of contents of the book. On the learning method online, click on the third year of physics, you can also dabble in...