Physics

Work and power direct current

Energy transformation mechanism in conductor with current. Forcing free media to move in the conductor, the attached electric field makes a job. According to the law of conservation of energy, perfect on the section of the chain, the work should be equal to the change in the energy of this area. Let the current in the conductor constant in time and is due to the ordered movement of electrons. Electric field Accelerates electrons, while doing work due to an external source. As a result of the collisions of electrons with ions crystal lattice The latter is transmitted part kinetic energy electrons, which leads to an increase in the energy of ion oscillations, i.e. To an increase in the internal energy of the conductor. This means that the temperature of the conductor increases, it heats up and begins to transmit energy to the environment. After a short time, thermal equilibrium is installed, i.e. Continuously entering the conductor energy due to the operation of the external source is transmitted to the surrounding bodies in the form of heat. The conductor itself is no longer heated.

Work and power of DC. Let the plot of the chain are under voltage U.. During D T. Through the cross section of the conductor is charged D q \u003d id t. The electric field makes the work A \u003d d qu.

From here: electric current

Equivalent are formulas:

Current power

(10.2)

The power distinguished on the resistors in the complex DC circuit depends on how these resistors are connected. With a sequential connection of the same current through resistors and power proportional to resistance. With a parallel connection, the same voltage and power is inversely proportional to the resistance.

Law of Joule Lenza. The amount of heat released by the conductor with the current in environment, defined formula

TKA operation- This is a job electric field By transfer electrical charges along the conductor;

The current operation on the plot of the chain is equal to the product of the current, voltage and time during which the work was performed.

Using the formula of the Ohm law for the circuit section, you can write several options for the formula for calculating the current operation:

According to the law of energy conservation:

the work is equal to the change in the energy of the circuit section, so the energy released by the conductor is equal to the current operation.

In the SI system:

Law of Joles -Lenza

When current over the conductor, the conductor is heated, and heat exchange with the environment, i.e. Explorer gives warmth around his bodies

The amount of heat released by the conductor with the current into the environment is equal to the product of the current of the current force, the resistance of the conductor and the time of passage through the conductor.

According to the law of maintaining energy, the amount of heat released by the conductor is numerically equal to the work that the current flows through the conductor during the same time.

In the SI system:

[Q] \u003d 1 J

DC power

The ratio of current operation during T to this time interval.

In the SI system:

Electrostatics and DC laws - Class! Naya Physics

Inquisitive

Footprints on the sand

If you had to walk around the beach at low tide, then you probably noticed that as soon as the leg steps on the wet hard sand, it immediately dries and whites around your track. Usually, this is explained by the fact that the water "squeezes" from the sand under the severity of the body. However, this is not the case, because the sand does not behave like a washcloth. Why whitewate sand? Will the sand stay white all the time while you are standing still?

It turns out ...
The peek on the beach first explained Reynold in 1885, he showed that the volume of sand increases when it is coming. Before that, the sands were "packed" the most dense way. Under the action of shift deformation, which occurs under the boot sole, the volume occupied by the sands, can only increase. While the sand level rises sharply, the water level can only rise as a result of capillary phenomena, and it takes time. Therefore, at the bottom of the foot trail of the sand, some time turns out to be higher than the water level - it is dry and white.