Advertisements
Advertisements
प्रश्न
A transformer converts 240 V AC to 60 V AC. The secondary has 75 turns. The number of turns in primary are _______.
(A) 600
(B) 500
(C) 400
(D) 300
उत्तर
∴ `N_p` = 300
APPEARS IN
संबंधित प्रश्न
State the principle on which transformer works.
Explain the construction and working of the transformer.
Derive an expression for ratio of e.m.f.s and currents in terms of number of turns in primary and secondary coil.
A power transmission line feeds input power at 2200 V to a step-down transformer with its primary windings having 300 turns. Find the number of turns in the secondary to get the power output at 220 V.
Find the ratio of primary and secondary currents in terms of turn ratio in an ideal transformer.
The primary coil of an ideal step-up transformer has 100 turns and the transformation ratio is also 100. The input voltage and power are 220 V and 1100 W, respectively. Calculate the
(a) number of turns in secondary
(b) current in the primary
(c) a voltage across secondary
(d) current in secondary
(e) power in secondary
Name the transformer used in the power transmitting station of a power plant.
Name two factors on which the magnitude of an induced e.m.f. in the secondary coil depends.
Name the phenomenon ?
Explain why an induced current must flow in such a direction so as to oppose the change producing it.
For what purpose are the transformers used? Can they be used with a direct current source?
Why is the iron core of a transformer made laminated (thin sheets) instead of being in one solid piece?
The input and output voltage of a transformer are 220 V and 44 V respectively. Find: the turns ratio.
Describe, with the help of a suitable diagram, the working principle of a step-up transformer. Obtain the relation between input and output voltages in terms of the number of turns of primary and secondary windings and the currents in the input and output circuits.
State the underlying principle of a transformer. How is the large scale transmission of electric energy over long distances done with the use of transformers?
Describe briefly, with the help of labelled diagram, working of a step-up transformer.
A step-up transformer converts a low voltage into high voltage. Does it not violate the principle of conservation of energy? Explain.
A transformer is used to step up an alternating emf of 200V to 440V. If the primary coil has 1000 turns, calculate the number of turns in the secondary coil.
In an ideal transformer, an output of 66 kV is required when an input voltage of 220 V is available. If the primary has 300 turns, how many turns should the secondary have?
State the principle of a transformer.
Can a transformer be used with direct current source? Give reason.
Name the principle on which functioning of a transformer depends.
What is the function of a step-up transformer?
(i) Draw a clear labelled diagram of an electric bell.
(ii) Explain in brief, its working.
(iii) What material is used for the core of an electric bell? State the reason.
Copy the given diagram of a transformer and complete it. Name the parts A and B. Name the part you have drawn to complete the diagram. What is the material of this part? Is this transformer a step-up or step-down? Give reason.
A transformer lowers e.m.f. 220 V to 12 volts. If the number of turns in primary are 8800, how many turns are in secondary coil?
Devices which is used to convert high alternating current to low alternating current is ______.
State whether true or false. If false, correct the statement.
A transformer can step up direct current.
In a transformer, the number of turns in the primary and the secondary are 410 and 1230 respectively. If the current in primary is 6A, then that in the secondary coil is
A step-down transformer reduces the supply voltage from 220 V to 11 V and increase the current from 6 A to 100 A. Then its efficiency is
Explain the construction of transformer.
Mention the various energy losses in a transformer.
Give the advantage of AC in long distance power transmission with an illustration.
The output power in step-up transformer used in practice is ______.
A transformer works on the principle of ______.
For an ideal step-down transformer, the quantity which is constant for both the coils is ______.
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.
Which of the following statement is true?
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.
If the secondary coil has a greater number of turns than the primary, ______.
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 the bulb is ______.
Define a Transformer.
Electrical energy is transmitted over large distances at high alternating voltages. Which of the following statements is (are) correct?
- For a given power level, there is a lower current.
- Lower current implies less power loss.
- Transmission lines can be made thinner.
- It is easy to reduce the voltage at the receiving end using step-down transformers.
In a transformer, number of turns in the primary coil are 140 and that in the secondary coil are 280. If current in primary coil is 4 A, then that in the secondary coil is ______.
The magnetic flux through a coil perpendicular to its plane is varying according to the relation Φ = (5t3 + 4t2 + 2t - 5) Weber. If the resistant of the coil is 5 ohm, then the induced current through the coil at t = 2 sec will be ______.
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 ______.
Magnetic flux passing through a coil is initially 4 × 10-4 Wb. It reduces to 10% of its original value in t second. If the emf induced is 0. 72 mV then t in second is ______.
The primary coil having NP turns of an ideal transformer is supplied with an alternating voltage VP. Obtain an expression for the voltage VS induced in its secondary coil having NS turns.
Mention two main sources of power loss in real transformers.
The large scale transmission of electrical energy over long distances is done with the use of transformers. The voltage output of the generator is stepped-up because of ______.
The primary coil of a transformer has 60 turns whereas its secondary coil has 3000 turns.
If a 220 V ac voltage is applied to the primary coil, how much emf is induced in the secondary coil?
How do the input and output powers in a transformer compare? State the assumption made.
