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Alternating Current — Physics STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 SciencePhysicsAlternating Current1 Mark
MCQ
Electrical energy is transmitted over large distances at high alternating voltages. Which of the following statements is (are) correct?
  • A
    For a given power level, there is a lower current.
  • B
    Lower current implies less power loss.
  • C
    Transmission lines can be made thinner.
  • D
    It is easy to reduce the voltage at the receiving end using step-down transformers.
✓

Answer

  1. For a given power level, there is a lower current.
  2. Lower current implies less power loss.
  1. It is easy to reduce the voltage at the receiving end using step-down transformers.

Solution:

Key Concept: Power loss due to transmisssion lines having resistance (R) and Irms current flowing in the circuit is I2rms R.

The power is to be transmitted over the large distances ar high alternating voltages, so current flowing through the wires will be low because of given power (P).

For a given power level, we find that

P = ErmsIrms (Irms is low when Erms is high)

Powor loss = I2rms R = low ($\because$ Irms is low)

Now at the receiving end high voltage is reduced by using step-down transformers.

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