Advertisements
Advertisements
प्रश्न
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.
Advertisements
उत्तर
Given:
NP = 40, eP = 100 V, PP = 100 watt, eS = 400 V
To find:
- Number of turns in the secondary (NS)
- Current in the secondary (IS)
- Current in the primary (IP)
Formulae:
- `"e"_"p"/"e"_"s" = "N"_"p"/"N"_"s"`
- P = Ie
Calculation:
From formula (i),
`"N"_"s" = "N"_"p" xx "e"_"s"/"e"_"p" = (40 xx 400)/100`
∴ NS = 160
For an ideal transformer, PS = PP
From formula (ii),
PS = ISeS
∴ IPeP = ISeS
∴ Is = `("I"_"p""e"_"p")/"e"_"s"`
= `"P"_"p"/"e"_"s" = 100/400 = 0.25` A
Ip = `"P"_"p"/"e"_"p"`
Ip = `100/100 = 1` A
∴ Ip = 1 A
- The number of turns in the secondary is 160.
- The current in the secondary is 0.25 A.
- The current in the primary is 1 A.
APPEARS IN
संबंधित प्रश्न
Derive an expression for ratio of e.m.f.s and currents in terms of number of turns in primary and secondary coil.
Write the function of a transformer.
Derive an expression for e.m.f. and current in terms of turns ratio
A power transmission line feeds input power at 2200 V to a step-down transformer with its primary windings having 300 turns. Find the number of turns in the secondary to get the power output at 220 V.
State the principle of the step-down transformer and its working.
Find the ratio of primary and secondary currents in terms of turn ratio in an ideal 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
Name two factors on which the magnitude of an induced e.m.f. in the secondary coil depends.
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.
Complete the following sentence :
……… energy is converted into …………energy by an electric motor.
How are the e.m.f in the primary and secondary coils of a transformer related with the number of turns in these coils?
What is the function of a transformer in an a.c. circuit? How do the input and output powers in a transformer compare?
A transformer is designed to work from a 240 V a.c. mains and to give a supply of 8 V to ring a house bell. The primary coil has 4800 turns. How many turns will be in the secondary coil?
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?
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 a transformer? On what principle does it work?
State the factors on which the frequency of the alternating e.m.f. depends.
Name three losses of energy in a transformer. How are they minimized?
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.
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?
What is Transformer?
Explain step up and step down transformer?
Describe the construction and working of a transformer with a neat labelled diagram.
Transformer works on ______.
State whether true or false. If false, correct the statement.
A transformer can step up direct current.
A step-down transformer reduces the supply voltage from 220 V to 11 V and increase the current from 6 A to 100 A. Then its efficiency is
Give the advantage of AC in long distance power transmission with an illustration.
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.
Power in primary coil is ______.
Define a Transformer.
A transformer is used ______
Draw the effective equivalent circuit of the circuit shown in figure, at very high frequencies and find the effective impedance.
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 ______.
Magnetic flux Φ in weber in a closed circuit of resistance 10Ω varies with time Φ (sec) as Φ = 6t2 - 5t + 1. The magnitude of induced current at t = 0.25s is ______.
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 ______.
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 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 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.
Explain why core of a transformer is always laminated.
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?
A 12 V, 60 W lamp is connected to 220 V AC via an ideal transformer. Find the primary current.
