Advertisements
Advertisements
प्रश्न
Describe the construction and working of a transformer with a neat labelled diagram.
Explain the working of a transformer with a neat labelled diagram.
Advertisements
उत्तर
Principle: It is based on the principle of mutual induction, i.e., whenever the magnetic flux linked with a coil changes, an e.m.f is induced in the neighbouring coil.
Construction: A transformer consists of two sets of coils, primary P and secondary S, insulated from each other. Coil P is called the input coil, and coil S is called the output coil. The two coils are wound separately on a laminated soft iron core.
Working: When an alternating 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 e.m.f. is induced in each coil. The amount of the magnetic flux linked with the coil depends upon the number of turns of the coil.
Let Φ be the magnetic flux linked per turn with both coils at a certain instant ‘t’. NP and NS be the number of turns of the primary and secondary coils, respectively.
Then at the instant t, the magnetic flux linked with the primary coil ΦP = NPΦ and with the secondary coil ΦS = NSΦ.
The induced emf in the primary and secondary coils will be:
ep = `-(d Phi_p)/(dt) = -N_p(d Phi)/(dt)` ...(1)
es = `-(d Phi_s)/(dt) = -N_s(d Phi)/(dt)` ...(2)
Dividing equation (2) by (1),
∴ `e_s/e_p = N_s/N_p` ...(3)
Equation (3) represents the equation of the transformer.
The ratio `N_s/N_p` is called the turns ratio (transformer ratio) of the transformer.
For an ideal transformer,
Input power = Output power
∴ ePIP = eSIS
∴ `e_s/e_p = I_p/I_s` ....(4)
From equations (3) and (4),
`e_s/e_p = N_s/N_p = I_p/I_s`
Notes
Students should refer to the answer according to their questions.
APPEARS IN
संबंधित प्रश्न
State the principle on which transformer works.
Express the turn ratio in terms of voltages.
State the principle of transformer working with the help of a diagram
Mention various energy losses in transformer device
Which coil of a step up transformer is made thicker and why?
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?
State two factors on which the magnitude of induced e.m.f. depend.
Name the phenomenon ?
Explain the significance of Lenz’s law to show the conservation of energy in electromagnetic induction.
What is the function of a transformer in an a.c. circuit? How do the input and output powers in a transformer compare?
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 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 ?
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.
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 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.
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.
A circular coil of 100 turns with a cross-sectional area of 1 m2 is kept with its plane perpendicular to the magnetic field of 1 T. The magnetic flux linkage is ______.
State the mathematical relation between a number of turns in the primary coil to a secondary coil in the step-up transformer.
Distinguish between Step up and Step Down Transformer.
The primary of a transformer has 40 turns and works on 100 V and 100 W. Find a number of turns in the secondary to step up the voltage to 400 V. Also calculate the current in the secondary and primary.
What are step-up and step-down transformers?
Explain the working of the transformer.
The 300 turn primary of a transformer has resistance 0.82 Ω and the resistance of its secondary of 1200 turns is 6.2 Ω. Find the voltage across the primary if the power output from the secondary at 1600V is 32 kW. Calculate the power losses in both coils when the transformer efficiency is 80%
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 ____________.
A 100% efficient transformer has 100 turns in the primary and 50 turns in its secondary coil. If the current in the secondary coil is 6 A, then the current in the primary coil is ______.
For an ideal step-down transformer, the quantity which is constant for both the coils is ______.
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 ______.
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 ______.
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.
The line that draws power supply to your house from street has ______.
- zero average current.
- 220 V average voltage.
- voltage and current out of phase by 90°.
- voltage and current possibly differing in phase `phi` such that `|phi| < pi/2`.
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)
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 ______.
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 ______.
An iron rod is placed parallel to magnetic field of intensity 2000 Am-1. The magnetic flux through the rod is 6 × 10−4 Wb and its cross-sectional area is 3 cm2. The magnetic permeability of the rod in Wb A-1m-1 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 ______.
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?
Derive the equation for a transformer.
For what purpose are the transformers used?
A 12 V, 60 W lamp is connected to 220 V AC via an ideal transformer. Find the primary current.
