Advertisements
Advertisements
Question
Explain the construction and working of the transformer.
Advertisements
Solution
Construction: It consists of two coils of primary and secondary coils insulated from each other and wound on a soft iron core as shown in fig. (a). Input is applied across the primary coil, and output is taken across the secondary coil.
Notations:
P1, P2: Primary coil
S1, S2: Secondary coil
There are two types of transformers:
- Step-up transformer: In this, the number of turns in the primary coil is less than the number of turns in the secondary coil. The primary coil is made up of thick wire, and the secondary coil is made up of thin wire.
- Step-down transformer: Here the number of turns in the primary coil is greater than that in the secondary coil. The secondary coil is made up of thick wire, and the primary coil is of thin wire.
Working: When an AC voltage is applied to the primary coil, the current through the coil goes on changing. Hence the magnetic flux through the core also changes. As this changing magnetic flux is linked with both coils, an emf is induced in each coil. The amount of magnetic flux linked with the coil depends upon the number of turns of the coil.
APPEARS IN
RELATED QUESTIONS
Draw a labeled diagram of a step-down transformer.
Derive an expression for e.m.f. and current in terms of turns ratio
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
Find the ratio of primary and secondary currents in terms of turn ratio in an ideal transformer.
Mention various energy losses in transformer device
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
Which coil of a step up transformer is made thicker and why?
Name the transformer used in the power transmitting station of a power plant.
What type of current is transmitted from the power station?
Name two factors on which the magnitude of an induced e.m.f. in the secondary coil depends.
The adjacent diagram shows a coil would around a soft iron bar XY. (a) State the polarity at the end X and Y as the switch is pressed. (b) Suggest one way increasing the strength of electromagnet so formed.
For what purpose are the transformers used? Can they be used with a direct current source?
The transformer is used in ______ current circuits.
The input and output voltage of a transformer are 220 V and 44 V respectively. Find: the turns ratio.
Mention the two characteristic properties of the material suitable for making core of a transformer.
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.
Can a transformer be used with direct current source? Give reason.
Why is the core of a transformer made of soft iron?
(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.
Distinguish between Step up and Step Down Transformer.
Transformer works on ______.
State whether true or false. If false, correct the statement.
A transformer can step up direct current.
In a series resonant RLC circuit, the voltage across 100 Ω resistor is 40 V. The resonant frequency ω is 250 rad/s. If the value of C is 4 µF, then the voltage across L is
What are step-up and step-down transformers?
Give the advantage of AC in long distance power transmission with an illustration.
Find out the phase relationship between voltage and current in a pure inductive circuit.
A 200V/120V step-down transformer of 90% efficiency is connected to an induction stove of resistance 40 Ω. Find the current drawn by the primary of the transformer.
A power transmission line feeds input power at 2300 V to a stepdown transformer with its primary windings having 4000 turns. What should be the number of turns in the secondary in order to get output power at 230 V?
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?
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.
For an LCR circuit, the power transferred from the driving source to the driven oscillator is P = I2Z cos φ.
- Here, the power factor cos φ ≥ 0, P ≥ 0.
- The driving force can give no energy to the oscillator (P = 0) in some cases.
- The driving force cannot syphon out (P < 0) the energy out of oscillator.
- 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.
A 60 W load is connected to the secondary of a transformer whose primary draws line voltage. If a current of 0.54 A flows in the load, what is the current in the primary coil? Comment on the type of transformer being used.
1 MW power is to be delivered from a power station to a town 10 km away. One uses a pair of Cu wires of radius 0.5 cm for this purpose. Calculate the fraction of ohmic losses to power transmitted if
- power is transmitted at 220 V. Comment on the feasibility of doing this.
- 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)
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 ______.
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.
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.
Explain why core of a transformer is always laminated.
How do the input and output powers in a transformer compare? State the assumption made.
An ideal transformer converts 170 V a.c. to 1.70 KV a.c. to transmit a power of 3.4 KW. If primary coil has 500 turns then alternating current in secondary coil is ______.
In an ideal transformer, the turns ratio is `N_p/N_s = 1/2`. The ratio Vs : Vp is equal to (the symbols carry their usual meaning):
On which principle is a transformer based?
On the basis of winding, what are the two types of transformers?
What does the laminated soft iron core provide for the flux?
How is the laminated soft iron core made?
Which description of the primary coil is correct?
What does the primary coil draw from the source?
Which description of the secondary coil is correct?
What is the induced EMF in the secondary coil?
What do \[V_s\] and \[V_p\] represent?
