Q102 / 160 · JIPMER 2004 · Physics

A lamp in which 10 amp current can flow at 15 V, is connected with an alternating source of potential 220 V. The frequency of source is 50 Hz. The inductance of choke coil required to light the bulb is

  • Correct answer
    A
    0.07 H
  • B
    0.14 H
  • C
    0.28 H
  • D
    1.07 H

Solution

The resistance of lamp $R=\frac{V}{I}=\frac{15}{10}=1.5 \Omega$ The impedance of circuit $Z=\frac{V}{I}=\frac{220}{10}=22 \mathrm{ohm}$ Again impedance $Z=\sqrt{R^2+\omega^2 L^2}$ or $\quad 22=\sqrt{(1.5)^2+(2 \times \pi \times 50)^2 L^2}$ or $\quad(22)^2=(1.5)^2+4 \pi^2 \times 50^2 \times L^2$ or $\quad L=0.07$ Henry

Hence, the correct answer is option: 'A'.

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