CLIL experienceContent and Language Integrated Learning

CLIL experienceContent and Language Integrated Learning

1st First lesson

Lenz's Law

When an emf is generated by a change in magnetic flux according to Faraday's Law, the polarity of the induced emf is such that it produces a current whose magnetic field opposes the change which produces it. The induced magnetic field inside any loop of wire always acts to keep the magnetic flux in the loop constant. In the examples below, if the B field is increasing, the induced field acts in opposition to it. If it is decreasing, the induced field acts in the direction of the applied field to try to keep it constant.

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

Faraday's Law

Any change in the magnetic environment of a coil of wire will cause a voltage (emf) to be "induced" in the coil. No matter how the change is produced, the voltage will be generated. The change could be produced by changing the magnetic field strength, moving a magnet toward or away from the coil, moving the coil into or out of the magnetic field, rotating the coil relative to the magnet, etc.

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

Faraday's law is a fundamental relationship which comes from Maxwell's equations. It serves as a succinct summary of the ways a voltage (or emf) may be generated by a changing magnetic environment. The induced emf in a coil is equal to the negative of the rate of change of magnetic flux times the number of turns in the coil. It involves the interaction of charge with magnetic field.

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

How Does an Electric Motor Work?

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

Induction Motor ActionInduction motors use shorted wire loops on a rotating armature and obtain their torque from currents induced in these loops by the changing magnetic field produced in the stator (stationary) coils.

• At the moment illustrated, the current in the stator coil is in the direction shown and increasing. The induced voltage in the coil shown drives current and results in a clockwise torque.

• Note that this simplified motor will turn once it is started in motion, but has no starting torque. Various techniques are used to produce some asymmetry in the fields to give the motor a starting torque.

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

Induction in Armature Coils

Induction motor action involves induced currents in coils on the rotating armature.

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

Movements

Turn

Turn

Complete

• Lenz’s Law says …• Faraday’s Law says …• In 1831 Michael Faraday was investigating

electric circuit and magnets when he found that a magnet could move a wire carrying current. This discovery is still used in all …

• It is possible to make a stronger motor by: 1. …

2. ...

3. …

Translate the following words:

Force ………………..

Loop ……………......

Magnetic field ………………..

Armature ………………..

Coil………………..

Winding ………………..

Torque………………..

Clockwise …………………..

Anticlockwise…………………..

To increase…………………..

To dicrease…………………..

Rotor…………………..

Stator…………………..

Fill the gaps

1. An electric current in a ………………………..……. Will experience a force;

2. The pair of forces creates a turning influence or ……………… to rotate the coil;

3. Motors have a several loops on an ……………………….. To provide a more ………………… torque;

4. How Does an Electric Motor Work? ………………………. ……………………………………………………………………. ……………………………………………………………………;

5. The magnetic field is produced by an ……………………. arrangement called ………………………………..

Translate the following questions and answer

• Come si produce il movimento del rotore in un motore a induzione? (come si forma la coppia?) ………………………… ……………………………………………………………………….………………………………………………………………………;

• Da cosa è prodotto il campo magnetico? ……………………… ………………………………………………………………………. ………………………………………………………………………;

• Il motore raffigurato si avvia? E in quale senso di marcia? ….. ………………………………………………………………………. ……………………………………………………………………….;