Presentation for lesson 1

to investigate the acting model of an electric engine and to explain the received results in a well-argued manner using Faraday's law of induction and Lentz's law.

1. The formula for induced EMF magnetic field.
2. In which case, the EMF induction will be maximum?
3. In which case, the EMF induction is zero?
4. The cause of EMF induction in a moving conductor
5.What is solenoid?
6.How are the lines of force directed inside and outside the solenoid?
7.The formula of the magnetic induction coil? What does it depend on?
8. What is called alternating current?
9. What is called direct current?

View video: Galileo. Experiment. Generator-engine
https://www.youtube.com/watch?v=Nfuz-bz9m-4

Faraday's experience confirmed the fundamental possibility of building an electric motor.
In 1834, B. S. Jacobi created the world's first DC electric motor, which implemented the principle of direct rotation of the movable part of the engine. In 1838, this engine (0.5 kW) was tested on the Neva river to propel a boat with passengers, i.e. received the first practical application.

A simple generator is a coil rotating between the poles of a magnet
The Principle of operation is based on the phenomenon of electromagnetic induction

When the coil rotates with a certain frequency, its sides cross the magnetic flux Ф and in each conductor is induced e. m. f. E

The simplest electric motor is a coil that rotates in a magnetic field.
The action of the engine is based on the Ampere law

If you connect the coil to a source of electrical energy, then an electric current will begin to pass through each of its conductors.
This current, interacting with the magnetic field of the poles, creates electromagnetic forces F.

When the current direction is selected, a force F directed to the right (according to the rule of the left hand) will act on the conductor located under the South pole, and a force F directed to the left will act on the conductor lying under the North pole.

1 – body (frame)
2 – stator (inductor)
On the pronounced poles of the stator (main poles) is the excitation winding, which is a constant current IV
3 – rotor (armature)
4 - armature winding, in which the rotation of the rotor is induced EMF.

This E. m. f. is removed from the armature winding by means of a sliding contact – brushes (5) included between the winding and the external circuit.
Sometimes additional poles are added to the main poles

To convert AC to DC, a collector is used.

The principle of its operation is as follows:
The ends of the coil are attached to two copper semi-rings (collector plates).
They are strengthened on the shaft of the machine and isolated from each other
On the plates are placed stationary brushes that give electrical energy to the consumer.

When rotating the coil, the collector plates rotate together with the shaft of the machine so that each brush touches one or the other plate.
The brushes on the collector are set so that they are moved from one plate to another at the moment when the EMF in the coil was equal to zero.

For better use of the armature winding individual turns are connected to each other in series.

Each collector plate is connected to the end of the previous and the beginning of the next turn.

Conclusion:Any DC machine can operate both in generator mode and in motor mode

high cost of manufacturing;
the need for preventive maintenance of collector-brush units;
limited life due to wear of the manifold.
(The last two shortcomings at the present stage of development of PTA are almost not noticeable).

Electric motors play a huge role in our modern life, if the electric motor had no light (application as a generator), there would be no water at home, since the electric motor is used in the pump, people could not lift heavy loads (use in a variety of cranes) …..

Multiple-choice tasks «Device DC machines»