Physics for junior high school, chapter 1 on electromagnetism, and summary of simple electromagnetic

Simple! First of all, electromagnetic induction means that an electric field can produce an electric current, and at the same time, an electric current can also produce a magnetic field! It's not about who works on whom! So, let's start with the first question:

1. You also know that the current is caused by the movement of electrons, so you should know the effect of the magnetic field on the electrons, which is the Lorentz force! The countless electrons are moving, and the Lorentz force is of course superimposed, so the superimposed force is the force of the magnetic field on the energized conductor rod.

2. Right. There is a magnetic field around the energized conductor, just like if you put a small magnetic needle on an energized conductor, the small magnetic needle will deflect! The current has no effect on the magnetic field, and if it has an effect, it is also a small effect, because the magnetic field around the energized conductor can only deflect the small magnetic needle, and the magnetic field can make the energized conductor rod move.

To add: the magnetic field has no effect on the electric current, because neither of them is an actual object, so how can it be used?

It can only be said that what is the effect of the magnetic field on the energized conductor rod, and what is the difference between the strength of the current and the magnetic field generated, obviously the stronger the current, the greater the magnetic field generated!

There is no such thing as a magnetic field acting on an electric current.

Magnetism is not the effect of the magnetic field on the current, but the phenomenon that the changing magnetic field causes the closed loop to produce an electric current.

is to generate an electric current and not to have an effect on it)

Generally speaking, the effect of the magnetic field on the electric current refers to the effect of the magnetic field on the force of the energized conductor.

There is a magnetic field around an energized conductor, which can be called electromagnetism.

If an energized conductor is placed in a magnetic field a, the effect of the current in the energized conductor on the magnetic field is a superposition of the magnetic field b present around the energized conductor on the magnetic field a.

Normally, high school doesn't allow you to superimpose two complex magnetic fields to calculate, so there is no such thing as the effect of electric current on magnetic fields.

1) First of all, remember "left-hand energy", "right-hand electricity".

Electricity + magnetism generates force, which changes from static, and the rule of the left hand; applied to motors;

Force + magnetism generates electricity, from movement to static, right-hand rule; applied to generators;

2) Secondly, the electric current produces a magnetic field, which is a matter of common sense, just like the earth has a gravitational pull, which should be known.

3) Thirdly, everything related to magnetic fields and currents can be called electromagnetic induction, and there is no need to divide them as you said.

1.If the circuit is closed and part of it moves in a magnetic field in a direction that is not the inductance line (cutting the inductance line), an electric current will be generated in the circuit.

If the circuit is closed and there is an electric current, part of which the current passes through the conductor in a magnetic field (not the magnetic field generated by the current), and the conductor is subjected to a force.

Only magnetic generation is electromagnetic induction, which is just an individual name.

2.A magnetic field is present around an energized conductor.

You'll understand it when you get to college.

Now you just need to be able to do the questions, and you don't need to understand.

Electromagnetic induction: the conductor coil cuts the magnetic inductance line in the magnetic field, and the current can be generated inside the conductor, which belongs to the magnetic electrogeny, that is, the effect of the magnetic field on the current, and the magnetism is used as a condition to generate electricity.

The effect of electric current on the magnetic field: that is, when the electricity is applied, a magnetic field is generated around the wire, and the electricity is used as a condition to generate magnetism.

1 If you just ask what the magnetic field does on the electric current, then it is the magnetic field that exerts a force on the conductor that is placed in it with an electric current, and this is how the electric motor works. Electromagnetic induction mainly refers to the magnetic generation of electricity, so that the conductor that does not pass the current moves in the magnetic field, and the two ends of the conductor will produce voltage, so the conductor is like a battery, and there will be a current output when the two ends are turned on, which is the working principle of the generator.

2 In fact, the electric current has no effect on the magnetic field, the electric current can produce a magnetic field, that is, a magnetic field exists around the energized conductor.

There is a magnetic field around the energized conductor and the current produces a magnetic field as simple as this o( o

Electromagnetic induction uses a magnetic field to generate an electric current (cutting magnetic inductance lines).

A magnetic field can change the direction of an electric current.

1. Magnetic phenomena:

1. Magnetism: the property of magnets that can attract iron, cobalt, nickel and other substances (iron absorption).

2. Magnet: Definition: A substance with magnetic properties.

Classification: Permanent magnets are divided into natural magnets and artificial magnets.

3. Magnetic pole: Definition: The most magnetic part of the magnet is called the magnetic pole. (The magnet is strongest at both ends and the weakest in the middle).

Type: A magnet that rotates freely in the horizontal plane, the magnetic pole of the guide is called the south pole (S), and the magnetic pole pointing to the north is called the north pole (n).

Law of action: the magnetic poles of the same name repel each other, and the magnetic poles of different names attract each other.

4. Magnetization: Definition: The process of making an object that was originally not magnetically magnetic.

Magnetization of steel and soft iron: After soft iron is magnetized, the magnetism tends to disappear and is called soft magnetic material. After the steel is magnetized, the magnetic properties are maintained for a long time and are called hard magnetic materials.

2. Magnetic field: 1. Definition: The substance that exists around the magnet is a special substance that cannot be seen or touched.

2. Basic properties: the effect of the magnetic field on the force generated by the magnet placed in it. The interaction between the magnetic poles occurs through the magnetic field.

3. Direction regulation: At a certain point in the magnetic field, the direction of the magnetic force pointed by the north pole of the small magnetic needle when it is stationary (the direction of the magnetic force experienced by the north pole of the small magnetic needle) is the direction of the magnetic field at that point.

4. Magnetic induction line:

Definition: Draw some directional curves in a magnetic field. The direction of the curve at any point is the same as the direction pointed by the North Pole of the magnetic needle placed at that point.

Direction: The magnetic inductance lines around the magnet all come out of the north pole of the magnet and return to the south pole of the magnet.

5. Magnetic pole force: At a certain point in the magnetic field, the direction of the magnetic force on the North Pole is consistent with the direction of the magnetic field at the point, and the direction of the magnetic force on the South Pole is opposite to the direction of the magnetic field at the point.

6. Classification: , Geomagnetic field:

Definition: The magnetic field that exists in the space around the earth, and the magnetic needle guides north because it is affected by the geomagnetic field.

Magnetic pole: The north pole of the geomagnetic field is near the south pole of geography, and the south pole of the geomagnetic field is near the north pole of geography.

Magnetic declination: first discovered by Shen Kuo in the Song Dynasty of China.

The magnetic field of the electric current:

Oersted experiment: There is a magnetic field around the energized wire, which is called the magnetic effect of the electric current. The phenomenon was discovered in 1820 by the Danish physicist Oersted. This phenomenon shows that there is a magnetic field around the energized wire, and the magnetic field is related to the direction of the current.

Magnetic field of energized solenoids: The magnetic field of energized solenoids is the same as that of bar magnets. The polarity of the two ends is related to the direction of the current, and the relationship between the direction of the current and the magnetic pole can be judged by the Ampere's rule.

Application: Electromagnets.

3. Electromagnetic induction:

1. Academic history: British physicist Faraday discovered.

2. Induced current:

The direction of the induced current in a conductor is related to the direction of motion and the direction of the magnetic field.

4. Application - alternator.

5. Alternating current and direct current:

Fourth, the effect of magnetic field on electric current:

1. The direction of force on the energized conductor in the magnetic field is related to the direction of the current and the direction of the magnetic field.

2. Application - DC motor.

Analyzing the circuit, it is obtained: two bulbs are connected in parallel, the voltmeter measures the power supply voltage, the ammeter A1 measures the total current, and the ammeter A2 measures the current through L2.

1) The indication of the voltmeter is equal to the power supply voltage, which is equal to 6V (L1, L2 in parallel, L1 emits light normally, U(L1)=U(L2)=U=6V).

2) R2 = (U2 squared) P2 = 12 * 12 4 = 36 Ammeter A2 indicator = I(L2) = U(L2) R2 = 6 36 = 1 6A = 3) L2 actual power = L2 current * L2 voltage =

w = l2 actual power * time = 1w * 60 seconds = 60j

Can you give a clearer picture?,I really can't see which is L1, which is L2, which is Power Construction S!

It's a really difficult question!

a. Whether there is obvious deflection is a question of the size of the induced current. The factors that affect the magnitude of the induced current are the magnitude of the speed at which the wire is cut; the direction of the speed of the wire cutting; the strength of the permanent magnet; the number of wires cut; Independent of cross-sectional area.

Personally, I think that no matter the thickness of the copper wire, as long as he cuts the magnetic inductance line in the magnetic field, it will generate an induced current, which has nothing to do with the thickness of the copper wire.

PS: The influencing factors should be the strength of the magnetic field and the frequency of cutting the magnetic inductance lines. ）

Because the range of the ammeter you choose is too large and the induced current is small, the ammeter does not deflection.

It should be connected to the microampere meter, so the i pointer is not deflected, the main reason is that the current is small.

The reason why you can't choose B: Do you think that the resistance of the thin copper wire is too large, so the induced current is too small? For a very short length of copper wire, the resistance of the thick and thin points is close to 0, which has no effect.

The induced current has nothing to do with the cross-sectional area A copper wire cutting the magnetic inductance line produces so much current, and two copper wires cutting separately also produces such a large current, so what about cutting two copper wires together? Of course, it's such a large current, understand?

The heating circuit is mainly composed of a temperature-sensing soft magnet and a permanent magnet. The temperature sensitive soft magnet is fixed with the heating surface, and the heat at the bottom of the inner pot is directly transferred to it through the heating surface, when the temperature is lower than 103, the temperature sensitive soft magnet is the same as the permanent magnet, and when the temperature is higher than 103, the temperature sensitive soft magnet will suddenly lose its magnetism.

When cooking, press the start switch with your hand, and make the permanent magnet and the temperature sensitive soft magnet attract through the transmission rod, and its suction force is greater than the elastic force of the spring and the gravity of the permanent magnet, so the permanent magnet will not fall, the contact is closed, the circuit is turned on, and the heating plate begins to heat up. When the rice is cooked, the moisture decreases, the temperature continues to rise from 100, when it reaches 103, the temperature sensing soft magnet loses its magnetism, and the permanent magnet falls under the action of gravity and spring, and the contacts are separated by the transmission rod, the circuit is disconnected, and the heating plate stops heating. In this way, it acts as a temperature limiter.

When the temperature drops, the bimetal sheet gradually recovers, when the temperature is lower than the holding temperature of 70, the position of the moving piece is lower than the position of the fulcrum, and the contact is closed under the action of the energy storage shrapnel, and the circuit is turned on. In this way, although the thermostat is disconnected, the constant action of the warmer can achieve the purpose of heat preservation.

Commemoration of the 117th anniversary of the birth of ***!!

When the temperature is below 103, the magnet is as magnetic as the permanent magnet, and when the temperature is higher than 103, the soft magnet will suddenly lose its magnetism.

1. The rod can be suspended with a thin wire so that it can rotate freely in the horizontal plane, and after stopping the rotation, it is a magnetic iron rod that points north and south. When it stops rotating, it stops in a random position and is a non-magnetic iron rod.

2. Use a coil to connect with the galvanometer to form a closed circuit, and then quickly insert the rod into the coil, and the galvanometer refers to the magnetic iron rod that has swing, otherwise it is a non-magnetic iron rod.