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महाराष्ट्र राज्य शिक्षण मंडळएचएससी विज्ञान (सामान्य) इयत्ता १२ वी

Explain step up and step down transformer?

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प्रश्न

Explain step up and step down transformer?

थोडक्यात उत्तर
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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

State the principle on  which transformer works.


Find the ratio of primary and secondary currents in terms of turn ratio in an ideal transformer.


State the principle of transformer working with the help of a diagram


Name the transformer used in the power transmitting station of a power plant.


What type of current is transmitted from the power station?


How is the e.m.f. across primary and secondary coils of a transformer related with the number of turns of the coil in them?


Why is the core of a transformer laminated?


State two ways through which the strength of an electromagnet can be increased.


State two factors on which the magnitude of induced e.m.f. depend.


The secondary windings of a transformer in which the voltage is stepped down are usually made of thicker wire than the primary. Explain why.


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


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


Given the input current 15 A and the input voltage of 100 V for a step-up transformer having 90% efficiency, find the output power and the voltage in the secondary if the output current is 3 A.  


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.


What is the turns ratio i.e., transformer ratio, ns: np, in an ideal transformer which in-creases ac voltage from 220 V to 33000 V?


What is the ideal transformer? 


What is a transformer? On what principle does it work?


State the principle of a transformer.


Can a transformer be used with direct current source? Give reason.


Why is the core of a transformer made of soft iron?


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?


The primary and secondary coils of a transformer each have an inductance of 200 x 10-6 H. The mutual inductance between the windings is 4 x 10-6 H. What percentage of the flux from one coil reaches the other?


Explain the construction of transformer.


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


A step-up transformer has 300 turns of primary winding and 450 turns of secondary winding. A primary is connected to 150 V and the current flowing through it is 9A. The current and voltage in the secondary are 


The output power in step-up transformer used in practice is ______.


Assertion: A transfonner cannot work on D.C. supply.

Reason: D.C. changes neither in magnitude nor in direction.


The transformation ratio in the step-up transformer is ______.

Eddy currents in the core of transformer can't be developed by ______.

The transformer voltage induced in the secondary coil of a transformer is mainly due to ______.

Which among the following, is not a cause for power loss in a transformer?


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.

A power transmission line feeds input power at 2300 V to a step down transformer with its primary windings having 4000 turns. The number of turns in the secondary in order to get output power at 230 V are ______.


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.

Power in primary coil is ______.


For an LCR circuit, the power transferred from the driving source to the driven oscillator is P = I2Z cos φ.

  1. Here, the power factor cos φ ≥ 0, P ≥ 0.
  2. The driving force can give no energy to the oscillator (P = 0) in some cases.
  3. The driving force cannot syphon out (P < 0) the energy out of oscillator.
  4. The driving force can take away energy out of the oscillator.

Draw the effective equivalent circuit of the circuit shown in figure, at very high frequencies and find the effective impedance.


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 ______.


Two coils P and Q are kept near each other. When no current flows through coil P and current increase in coil Q at the rate 10A/s, the emf in coil P is 15mV. When coil Q carries no current and current of 1. 8A flows through coil P, the magnetic flux linked with the coil Q 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 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.


Efficiency of transformer is the ratio of ______.


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.


Derive the equation for a transformer.


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


In an ideal transformer, the turns ratio is \[\frac {N_p}{N_s}\] = \[\frac {1}{2}\]. The ratio Vs : Vp is equal to (the symbols carry their usual meaning) ______.


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?


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