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7. Alternating current — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics7. Alternating current1 Mark
MCQ
For $L - R$ circuit, the time constant is equal to
  • ✓
    twice the ratio of the energy stored in the magnetic field to the rate of the dissipation of energy in the resistance.
  • B
    the ratio of the energy stored in the magnetic field to the rate of dissipation of energy in the resistance.
  • C
    half of the ratio of the energy stored in the magnetic field to the rate of dissipation of energy in the resistance.
  • D
    square of the ratio of the energy stored in the magnetic field to the rate of dissipation energy in the resistance.
✓

Answer

Correct option: A.
twice the ratio of the energy stored in the magnetic field to the rate of the dissipation of energy in the resistance.
a
The time required for the current flowing in the $LR$ series circuit to reach its maximum steady state value is equivalent to about $5$ time constants or $5 t.$ This time constant $\tau,$ is measured by $\tau=L / R,$ in seconds, where $R$ is the value of the resistor in ohms and Lis the value of the inductor in Henries

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