16. Operation carried out in Thermal power station?
Ans:
The water is obtained in the
boiler and the coal is burnt so that steam is obtained this steam is allowed to
hit the turbine , the turbine which is coupled with the generator generates the
electricity
17. State the difference between generator and alternator
Ans:
Generator and alternator are two
devices, which converts mechanical energy into electrical energy. Both have the
same principle of electromagnetic induction, the only difference is that their
construction. Generator persists stationary magnetic field and rotating
conductor which rolls on the armature with slip rings and brushes riding
against each other, hence it converts the induced emf into dc current for
external load whereas an alternator has a stationary armature and rotating
magnetic field for high voltages but for low voltage output rotating armature
and stationary magnetic field is used.
18. What is difference between fuse and breaker?
Ans:
Fuses are burned at the time of
over current flows in the circuit but breakers are just open(not burn) at the
time of over current flow. Fuses are used in only one time but breakers are
used by multiple number of times.
19. Brief description about Transformer?
Ans:
A transformer is a device that
changes (transforms) and alternating potential difference (voltage) from one
value to another value be it smaller or greater using the principle of
electromagnetic induction.
20. Briefly explain different types of Transformers?
Ans:
Step-up Transformer
On a step-up transformer there
are more turns on the secondary coil than the primary coil. The induced voltage
across the secondary coil is greater than the applied voltage across the
primary coil or in other words the voltage has been “stepped-up”.
Step-down Transformer
A step down transformer has less
turns on the secondary coil that the primary coil. The induced voltage across
the secondary coil is less the applied voltage across the primary coil or in
other words the voltage is “stepped-down”.
21. Explain different losses in a transformer.
Ans:
There are two types of losses
occurring in transformer:
• Constant losses or Iron losses:
The losses that occur in the core are known as core losses or iron losses. Two
types of iron losses are:
o eddy current loss
o Hysteresis loss.
These losses depend upon the
supply voltage, frequency, core material and its construction. As long as
supply voltage and frequency is constant, these losses remain the same whether
the transformer is loaded or not. These are also known as constant losses.
• Variable losses or copper
losses: when the transformer is loaded, current flows in primary and secondary
windings, there is loss of electrical energy due to the resistance of the
primary winding, and secondary winding and they are called variable losses.
These losses depend upon the loading conditions of the transformers. Therefore,
these losses are also called as variable losses.
22. Explain Power factor?
Ans:
The power factor of an AC
electrical power system is defined as the ratio of the real power flowing to
the load to the apparent power in the circuit.
23. State Ohm's Law?
Ans:
Ohm's law states that the
electrical current (I) flowing in an circuit is proportional to the voltage (V)
and inversely proportional to the resistance (R). Therefore, if the voltage is
increased, the current will increase provided the resistance of the circuit
does not change.
24. State
Ans:
Kirchhoff's law 1 : states that the voltage changes around a
closed path in a circuit add up to zero, where the voltage change DV = emf in
going through a battery from - terminal to + terminal is considered to be
positive, and the voltage change DV = I R in going through a resistor in the
assumed direction of the current I is considered to be negative.
Kirchhoff's law 2 : states that the sum of the currents entering
any node (i.e., any junction of wires) equals the sum of the currents leaving
that node.
25. State Maximum power transfer theorem?
Ans:
The Maximum power transfer theorem explains about the load that a
resistance will extract from the network. This includes the maximum power from
the network and in this case the load resistance is being is equal to the
resistance of the network and it also allows the resistance to be equal to the
resistance of the network. This resistance can be viewed by the output
terminals and the energy sources can be removed by leaving the internal
resistance behind.
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