Advertisements
Advertisements
Question
What is Transformer?
Advertisements
Solution
The transformer is an electrical device that converts low alternating voltage at high current to high alternating voltage at low current and vice-versa.
RELATED QUESTIONS
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.
On which type of current do transformers work?
You are required to make an electromagnet from a soft iron bar by using a cell, an insulated coil of copper wire and a switch. (a) Draw a circuit diagram to represent the process. (b) label the poles of the electromagnet.
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.
State two ways through which the strength of an electromagnet can be increased.
Name the phenomenon ?
Explain the significance of Lenz’s law to show the conservation of energy in electromagnetic induction.
For what purpose are the transformers used? Can they be used with a direct current source?
How are the e.m.f in the primary and secondary coils of a transformer related with the number of turns in these coils?
Why is the iron core of a transformer made laminated (thin sheets) instead of being in one solid piece?
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.
Describe briefly and two energy losses, giving the reasons for their occurrence in actual transformers ?
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.
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. from 220 V to 15 V. If the number of turns in primary are 3520, how many turns are in the 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?
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 ______
Describe the construction and working of a transformer with a neat labelled diagram.
Transformer works on ______.
Devices which is used to convert high alternating current to low alternating current is ______.
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
Find out the phase relationship between voltage and current in a pure inductive circuit.
A 220 V input is supplied to a transformer. The output circuit draws a current of 2.0 A at 440 V. If the ratio of output to input power is 0.8, then the current drawn by primary winding is ______.
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 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?
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.
Which of the following statement is true?
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.
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.
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)
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.
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.
Derive the equation for a transformer.
What type of transformer is used in a mobile phone charger?
For what purpose are the transformers used?
How do the input and output powers in a transformer compare? State the assumption made.
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?
What does the laminated soft iron core provide for the flux?
Why is soft iron used in the core?
Which winding is the output coil connected to the load?
Which law relates the changing flux to the EMF induced in both coils?
What is the induced EMF in the secondary coil?
