Advertisements
Advertisements
Question
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
Solution
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
RELATED QUESTIONS
State the principle on which transformer works.
Derive an expression for ratio of e.m.f.s and currents in terms of number of turns in primary and secondary coil.
Draw a labeled diagram of a step-down transformer.
Express the turn ratio in terms of voltages.
How much current is drawn by the primary of a transformer connected to 220 V supply when it delivers power to a 110 V − 550 W refrigerator?
Mention various energy losses in transformer device
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?
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.
Explain why an induced current must flow in such a direction so as to oppose the change producing it.
For what purpose are the transformers used? Can they be used with a direct current source?
The secondary windings of a transformer in which the voltage is stepped down are usually made of thicker wire than the primary. Explain why.
Why is the iron core of a transformer made laminated (thin sheets) instead of being in one solid piece?
The transformer is used in ______ current circuits.
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.
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.
The input and output voltages of a transformer are 220 V and 44V respectively. Find the current in input circuit if the output current is 2 A.
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?
What is the function of a step-up transformer?
Why is the core of a transformer made of soft iron?
Draw a labelled diagram to show the various parts of a step-up transformer and step down transformer.
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?
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?
Describe the construction and working of a transformer with a neat labelled diagram.
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 step-down transformer connected to the main supply of 220 V is used to operate 11V,88W lamp. Calculate
- Voltage transformation ratio and
- Current in the primary
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?
For an ideal step-down transformer, the quantity which is constant for both the coils is ______.
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?
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 current in the bulb 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 ______.
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`.
Draw the effective equivalent circuit of the circuit shown in figure, at very high frequencies and find the effective impedance.
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 ______.
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 ______.
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.
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.
What is a transformer?
Explain why core of a transformer is always laminated.
