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प्रश्न
State the principle of the step-down transformer and its working.
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उत्तर
Principle: A transformer is based on the principle of electromagnetic mutual induction, i.e., whenever the amount of magnetic flux linked with a coil changes, an e.m.f. is induced in the neighboring coil.
Working
Alternating emf is supplied to the primary coil PP’. The resulting current induces a current in the secondary coil.
Magnetic flux linked with primary is also linked with the secondary. The induced emf in each turn of the secondary is equal to that induced in each turn of the primary.
Let
EP − Alternating emf applied to primary
nP − Number of turns in the primary
`(dphi)/dt-"Rate of change of flux through each turn of primary coil"`
`:.E_p=-n_p (dphi)/dt" ......(1)"`
Es− Alternating emf of secondary
ns − Number of turns in secondary
`:.E_s=-n_s (dphi)/dt" ....(2)"`
Dividing equation (2) by (1),
`E_s/E_p=n_s/n_p=k`
For step-up transformer, K > 1
∴ Es > Ep
For step-down transformer, K < 1
∴ Es < Ep
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संबंधित प्रश्न
State the principle on which transformer works.
State two factors on which the magnitude of induced e.m.f. depend.
Name two kind of energy loss in a transformer. How is it minimized?
What is a transformer? On what principle does it work?
The power supply to the primary coil of a transformer is 200 W. Find
(i) Current in primary coil if the e.m.f. supply to it is equal to 220V.
(ii) The number of turns in the primary coil is equal to 80 and that in secondary is 800. What is the transformation ratio?
(iii) Name the type of transformer.
(iv) What will be the output voltage?
(v) What is the current in the secondary coil for an ideal transformer?
(vi) What is the output power?
(vii) Is output and input power equal?
(viii) Compare the current flowing in a secondary coil and in a primary coil.
State whether true or false. If false, correct the statement.
A transformer can step up direct current.
Read the following paragraph and answer the question:
Long distance power transmissions
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.
We need to step-up the voltage for power transmission, so that ______.
A transformer is essentially an a.c. device. It cannot work on d.c. It changes alternating voltages or currents. It does not affect the frequency of a.c. It is based on the phenomenon of mutual induction. A transformer essentially consists of two coils of insulated copper wire having different numbers of turns and wound on the same soft iron core.
The number of turns in the primary and secondary coils of an ideal transformer is 2000 and 50 respectively. The primary coil is connected to a main supply of 120 V and secondary coil is connected to a bulb of resistance 0.6 Ω.
The value of current in primary coil is ______.
Draw the effective equivalent circuit of the circuit shown in figure, at very high frequencies and find the effective impedance.
Magnetic flux Φ in weber in a closed circuit of resistance 10Ω varies with time Φ (sec) as Φ = 6t2 - 5t + 1. The magnitude of induced current at t = 0.25s is ______.
