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प्रश्न
Describe the construction and working of a transformer with a neat labelled diagram.
Explain the working of a transformer with a neat, labelled diagram.
उत्तर
Principle:
It is based on the principle of mutual induction, i.e., whenever the magnetic flux linked with a coil changes, an e.m.f is induced in the neighbouring coil.
- Construction:
a. A transformer consists of two sets of coils, primary P and secondary S, insulated from each other. Coil P is called the input coil, and coil S is called the output coil.
b. The two coils are wound separately on a laminated soft iron core.
- Working:
a. When an alternating voltage is applied to the primary coil, the current through the coil goes on changing. Hence, the magnetic flux through the core also changes.
b. As this changing magnetic flux is linked with both the coils, an e.m.f is induced in each coil.
c. The amount of the magnetic flux linked with the coil depends upon the number of turns of the coil.
d. Let, ‘Φ’ be the magnetic flux linked per turn with both the coils at a certain instant ‘t’.
e. Let ‘NP' and ‘NS’ be the number of turns of the primary and secondary coil,
NPΦ = magnetic flux linked with the primary coil at a certain instant ‘t’
NSΦ = magnetic flux linked with the secondary coil at a certain instant ‘t’
f. Induced e.m.f produced in the primary and secondary coil is given by,
`"e"_"p" = -("d"phi_"p")/"dt" = -"N"_"p"("d"phi)/"dt"` ….(1)
`"e"_"s" = -("d"phi_"s")/"dt" = -"N"_"s"("d"phi)/"dt"` ….(2)
g. Dividing equation (2) by (1),
∴ `"e"_"s"/"e"_"p" = "N"_"s"/"N"_"p"` ….(3)
Equation (3) represents equation of transformer.
The ratio `"N"_"s"/"N"_"p"` is called turns ratio (transformer ratio) of the transformer.
h. For an ideal transformer,
Input power = Output power
∴ ePIP = eSIS
∴ `"e"_"s"/"e"_"p" = "I"_"p"/"I"_"s"` ….(4)
i. From equation (3) and (4),
`"e"_"s"/"e"_"p" = "N"_"s"/"N"_"p" = "I"_"p"/"I"_"s"`
Notes
Students should refer to the answer according to their questions.
APPEARS IN
संबंधित प्रश्न
Explain the construction and working of the transformer.
Draw a labeled diagram of a step-down transformer.
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(i) What device is used to bring the high voltage down to low voltage of a.c. current and what is the principle of its working ?
(ii) Is it possible to use this device for bringing down the high dc voltage to the low voltage? Explain
(iii) Write the values displayed by the students and the teacher.
Express the turn ratio in terms of voltages.
Name two factors on which the magnitude of an induced e.m.f. in the secondary coil depends.
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1) Name the device used to change the alternating voltage to a higher or lower value. State one cause for power dissipation in this device.
2) Explain with an example, how power loss is reduced if the energy is transmitted over long distances as an alternating current rather than a direct current.
3) Write two values each shown by the teachers and Geeta.
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Name three losses of energy in a transformer. How are they minimized?
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(v) What is the current in the secondary coil for an ideal transformer?
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Read the following paragraph and answer the question:
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Read the following paragraph and answer the question:
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The large-scale transmission and distribution of electrical energy over long distances is done with the use of transformers. The voltage output of the generator is stepped up. It is then transmitted over long distances to an area sub-station near the consumers. There the voltage is stepped down. It is further stepped down at distributing sub-stations and utility poles before a power supply of 240 V reaches our homes.
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Power in primary coil is ______.
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- a step-up transformer is used to boost the voltage to 11000 V, power transmitted, then a step-down transfomer is used to bring voltage to 220 V. (ρCu = 1.7 × 10–8 SI unit)
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If a current of 5A flows in the primary coil, how much current will flow in a load in the secondary coil? State the assumption you have made regarding the transformer, in this calculation.
What is a transformer?
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For what purpose are the transformers used?
