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प्रश्न
Give the advantage of AC in long distance power transmission with an illustration.
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उत्तर
- When power is transmitting for long-distance a fraction of power is lost due to joule heating (I2R).
- This power loss can be tackled either by reducing current i or by reducing resistance R of a transmission line.
- At the transmitting point, voltage is increased and the current is decreased by a step-up transformer.
- This reduced current at high voltage reaches the destination without applicable loss.
- At the receiving point, voltage is decreased and current is increased by step down transformer.
- Example 1:
2MW power is transmitted at 40Ω with 10 kV voltage
I = `"P"/"V" = (2 xx 10^6)/(10 xx 10^3)` = 200 A
Power loss = I2 R = (200)2 × 40 = 1.6 × 106 W
% of Power loss = `(1.6 xx 10^6)/(2 xx 10^6) xx 100 % = 80%` - Example 2:
When 2MW power at 40 Q is transmitted with 100 kV voltage.
I = `"P"/"V" = (2 xx 10^3)/(100 xx 10^3)` = 20 A
Power loss = I2 R = (200)2 × 40 = 0.016 × 106 W
% of power loss = `(0.016 xx 10^6)/(2 xx 10^6) xx 100%`
= 0.8 × 100% = 80%
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संबंधित प्रश्न
Write the function of a transformer.
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.
What type of current is transmitted from the power station?
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.
Applying e.m. f to primary coil is 210 V. If the number of turns in primary coil is 200 turns and that of in secondary coil is 20 turns, then find out the output voltage. Name the type of transformer.
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?
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 ______.
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.
A transformer consisting of 300 turns in the primary and 150 turns in the secondary gives output power of 2.2 kW. If the current in the secondary coil is 10 A, then the input voltage and current in the primary coil are ______.
