5 electrical measuring instruments, electric engines

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to explain the operating principle of electrical measuring instruments, electric engines;

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(T)(D) Teacher demonstration

Wind several turns of wire round a cork and hang it, from a clump, between the poles of magnet as shown. Pass a current briefly through the coil.

What happens?
Does the coil turn the opposite way if you reverse the current?
There are two ways to find the direction of rotation in the diagram:
Use Fleming’s Left Hand Rule for each side of the coil.
Find which end of the coil becomes a N-pole. This end will be attracted to the S-pole of the magnet.

This twisting movement is used in electric motors and in moving-coil ammeters and voltmeters (electrical measuring instruments).

GROUP 1: Working Principle of an Electric Motor
GROUP 2: Working Principle of Electrical measuring instruments
GROUP 3: Working Principle of an electric engines.

Basically, an electric motor is nothing more than a coil of wire, built onto an axle so that it can rotate within a magnetic field.
When current is switched on in the coil, the magnetic forces create a torque which rotates the coil.
In small, simple motors (such as in a child’s toy car) the magnetic field is provided by a permanent magnet. In more powerful motors, the field is provided by an electromagnet

The Rotor is the part that rotates. It is a coil of wire (or often several coils) mounted on an axle to allow rotation.
The Stator is the part that remains stationary. It may be a permanent magnet, or an electromagnet. Its
purpose is to provide the magnetic field.
The Brushes are fine, flexible metal wires, or (more commonly) a spring-loaded stick of graphite. The brushes maintain electrical contact onto the rotating metal ring.
The Commutator is a metal cylinder, split into 2 pieces. As it rotates, the direction of current in the coil is reversed every half-rotation. This way, the torque is always in the same rotational direction, even though the coil has turned over.

All electrical meters, ammeters and voltmeters, are based on a device called a “galvanometer”, named in honour of Luigi Galvani, one of the pioneers of Electrical Science.
The galvanometer works because of the Motor Effect; the more current that flows through its coil, the greater the torque on the coil, and the greater the deflection of the meter needle, working against a small spring . The needle then
points to a scale of measurements, which can be calibrated to read either current or voltage.

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What has been learned
What remained unclear
What is necessary to work on