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Explain step up and step down transformer? - Physics

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प्रश्न

Explain step up and step down transformer?

थोडक्यात उत्तर

उत्तर

  1. Step-up transformer:
    a.
    A transformer that converts a low voltage at high current into a high voltage at low current is called a step-up transformer.
    b. In a step-up transformer, the number of turns in secondary coil NS is greater than the number of turns in primary coil NP. In this transformer, eS > eP and IS < IP.  
    c. The primary coil is made from a thick insulated copper wire so that it can sustain the high current. The secondary coil is made of a thin insulated wire.
    d. Current through secondary is less than primary. 
  2. Step down transformer:
    a. A transformer which converts a high voltage at low current into a low voltage at high current is called a step-down transformer.
    b. In step down transformer, the number of turns in the secondary coil NS is less than the number of turns in the primary coil NP. In this transformer eS < eP and IS > IP.
    c. The primary coil is made of a thin insulated wire and the secondary coil is made from thick wire so that it can sustain the high current.  
    d. Current through primary is less than secondary. 
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पाठ 12: Electromagnetic Induction - Short Answer II

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संबंधित प्रश्‍न

Draw a labeled diagram of a step-down 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


What type of current is transmitted from the power station?


The teachers of Geeta’s school took the students on a study trip to a power generating station, located nearly 200 km away from the city. The teacher explained that electrical energy is transmitted over such a long distance to their city, in the form of alternating current (ac) raised to a high voltage. At the receiving end in the city, the voltage is reduced to operate the devices. As a result, the power loss is reduced. Geeta listened to the teacher and asked questions about how the ac is converted to a higher or lower voltage.

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.


On which type of current do transformers work?


Name the phenomenon ?


For what purpose are the transformers used? Can they be used with a direct current source?


In a transformer, the frequency of A.C. voltage ______. 


What is the function of a transformer in an a.c. circuit? How do the input and output powers in a transformer compare?


Name two kind of energy loss in a transformer. How is it minimized?


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.


Mention the two characteristic properties of the material suitable for making core of a transformer.


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?


State the principle of working of a transformer. Can a transformer be used to step up or step down a d.c. voltage? Justify your answer.


Draw a labeled diagram of a full wave rectifier circuit. State its working principle. Show the input-output waveforms ?


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. 


An a.c generator generates an emf 'ε' where ε = 314 Sin (50πt) volt. Calculate the frequency of emf ε.


State the principle of a transformer.


What is the function of a step-up transformer?


Name three losses of energy in a transformer. How are they minimized?


Draw a labelled diagram to show the various parts of a step-up transformer and step down transformer.


The primary coil of a transformer has 200 turns while the secondary coil has 1000 turns. What type of transformer is this? if the input voltage is 10V, what will be the output voltage?


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?


A transformer lowers e.m.f. from 220 V to 15 V. If 400 W power is given in primary, calculate (i) the current in primary coil and (ii) the current in secondary coil.


An ideal transformer has 100 turns in the primary and 250 turns in the secondary. The peak value of the AC is 28 V. The rms secondary voltage is nearest to ______ 


State the mathematical relation between a number of turns in the primary coil to a secondary coil in the step-up transformer. 


What is Transformer?


Describe the construction and working of a transformer with a neat labelled diagram.


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


Explain the construction of transformer.


Explain the working of the transformer.


Mention the various energy losses in a transformer.


Find out the phase relationship between voltage and current in a pure inductive circuit.


A transformer having efficiency of 80% is working on 200 V and 6 kW power supply. If the current in the secondary coil is 6 A, the voltage across the secondary coil and the current in the primary coil respectively are ____________.


The loss of energy in the form of heat in the iron core of a transformer 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, ______.


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 voltage across the secondary coil is ______.


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 ______.


Define a Transformer.


The primary coil of a transformer has 800 turns and the secondary coil has 8 turns. It is connected to a 220 V ac supply. What will be the output voltage?


The primary winding of a transformer has 100 turns and its secondary winding has 200 turns. The primary is connected to an a.c supply of 120 V and the current flowing in its is 10 A. The voltage and the current in the secondary are ______.


A step-down transformer connected to an ac mains supply of 220 V is made to operate at 11 V, 44 W lamp. Ignoring power losses in the transformer, what is the current in the primary circuit?


The line that draws power supply to your house from street has ______.

  1. zero average current.
  2. 220 V average voltage.
  3. voltage and current out of phase by 90°.
  4. voltage and current possibly differing in phase `phi` such that `|phi| < pi/2`.

A transformer operating at primary voltage 8 kV and secondary voltage 160 V serves a load of 80 kW. Assuming the transformer to be ideal with purely resistive load and working on unity power factor, the loads in the primary and secondary circuit would be:


A transformer consisting of 300 turns in the primary and 150 turns in the secondary gives output power of 2.2 kW. If the current in the secondary coil is 10 A, then the input voltage and current in the primary coil are ______.


An ideal transformer converts 220 V a.c. to 3.3 kV a.c. to transmit a power of 4.4 kW. If primary coil has 600 turns, then alternating current in secondary coil 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 ______.


An iron rod of 0.2 cm2 cross-sectional area is subjected to a magnetising field of 1200 Am-1. If the susceptibility of iron is 599, then the magnetic flux produced is ______.


The self-inductance of a closely wound coil of 200 turns is 10 mH. Determine the value of magnetic flux through the cross-section of the coil when the current passing through the coil is 4 mA.


The primary coil of a transformer has 60 turns whereas its secondary coil has 3000 turns.

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?


How do the input and output powers in a transformer compare? State the assumption made.


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