Advertisements
Advertisements
Question
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
Advertisements
Solution
(a) Number of turns in secondary coil is given by
`N_S/N_P=n`
`=>N_S/100=100`
⇒NS=10,000
(b) Current in primary is given by
IPVP=P
`=>I_P=1100/220=5A`
(c) Voltage across secondary is given by
`V_S/V_P=N_S/N_P=n`
⇒VS=100×220=22,000 V
(d) Current in secondary is given by
VSIS=P
`=>I_S=P/V_S=1100/22000=0.05A`
(e) Power in secondary is power in primary in an ideal transformer.
= 1,100 W
RELATED QUESTIONS
A group of students while coming from the school noticed a box marked "Danger H.T. 2200 V" at a substation in the main street. They did not understand the utility of a such a high voltage, while they argued, the supply was only 220 V. They asked their teacher this question the next day. The teacher thought it to be an important question and therefore explained to the whole class.
Answer the following questions:
(i) What device is used to bring the high voltage down to low voltage of a.c. current and what is the principle of its working ?
(ii) Is it possible to use this device for bringing down the high dc voltage to the low voltage? Explain
(iii) Write the values displayed by the students and the teacher.
How is the e.m.f. across primary and secondary coils of a transformer related with the number of turns of the coil in them?
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?
Name three losses of energy in a transformer. How are they minimized?
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
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 ____________.
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 ______.
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.
Which winding is the output coil connected to the load?
Assuming no flux leakage, which coils does the changing flux thread through?
