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प्रश्न
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.
विकल्प
a, b and c
a, b and d
b, c and d
c and d
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उत्तर
a, b and d
Explanation:
As we know that power = `I_(rms)^2R`
So to decrease power loss Irms and R must be lower for a constant power supply. To decrease Irms, Vrms must be increased by step up transformer to get same power in step-up transformer
For a given power level, we find that
P = ErmsIrms ......(Irms is low when Erms is high)
Power loss = `I_(rms)^2` R = low ......(∵ Irms is low)
Now at the receiving end, high voltage is reduced by using step-down transformers.
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संबंधित प्रश्न
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.
A transformer converts 240 V AC to 60 V AC. The secondary has 75 turns. The number of turns in primary are _______.
(A) 600
(B) 500
(C) 400
(D) 300
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