Electrical & Electronics Engineering Questions Pdf - 1

Applications of Superconductors are

1. Superconductors are used for the production of strong magnetic fields required in power generators.

2. Magnetic-levitation is an application where superconductor material can be suspended in air against repulsive force from a permanent magnet. This is used in transportation particularly in train, eliminating friction between train and its tracks.

3. Superconductors are recently used for creation of strong magnetic fields for transformers, motors, generators, transmission systems etc. Superconductor fuses, breakers, rectifiers, electronic filters are also being researched and are used in great now-a-days.

4. In nuclear physics also, superconductors are used in controlled fusion reactors and in particle accelerometers.

5. The zero resistivity characteristics of superconductors make them an ideal material for lossless d.c. power transmission systems.

6. The phenomenon of superconductivity is also used in MRI (Magnetic Resonance Imaging) devices in field of medicine for diagnosis.

7. Superconducting solenoids are also made which produce higher magnetic induction as compared to iron core electromagnets.

8. Information storage functions and logic functions can be performed in computers with the help of superconductors.

9. Superconducting Quantum Interface Devices (SQUIDS) are used in the field of medicine to measure the weak fields generated by heart and brain.

10. Cryoton, which is an important application of superconductor, is a switching device which use the principle of destruction of superconductivity by the application of magnetic fields exceeding the critical value.

When voltage is applied in a circuit it causes current (i.e. movement of free electrons) to flow through it. Clearly, work is being done in moving the electrons in the circuit.

Stepper motor is the electrical machine which act upon input pulse applied to it. It is one type of synchronous motor which runs in steps in either direction instead of running in complete cycle. So, in automation parts it is used.

There are three types of system

Closed system

Open system

Isolated system

An induction machine consists of two parts the stator and the rotor. The stator has three phase winding made of copper and conductors. The rotors are of two types

Phase wound rotor

Squirrel cage rotor

The Phase wound rotor windings are made up of copper and are connected to slip rings which are made up of either brass or phosphorous bronze.

In case of squirrel cage rotors, copper bares are placed in the rotor slots. These rotors bars are short circuited at each end by solid end rings made up of copper brass or aluminium.