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MHT CET · Physics · Alternating Current

The a.c. source is connected to series LCR circuit. If voltage across \(\mathrm{R}\) is \(40 \mathrm{~V}\), that across \(\mathrm{L}\) is \(80 \mathrm{~V}\) and that across \(\mathrm{C}\) is \(40 \mathrm{~V}\), then the e.m.f. 'e' of a.c. source is

  1. A \(40 \mathrm{~V}\)
  2. B \(40 \sqrt{2} \mathrm{~V}\)
  3. C \(80 \mathrm{~V}\)
  4. D \(160 \mathrm{~V}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(40 \sqrt{2} \mathrm{~V}\)

Step-by-step Solution

Detailed explanation

The emf across the AC source is given as:
\(\mathrm{e} =\sqrt{\left(\mathrm{V}_{\mathrm{K}}\right)^2+\left(\mathrm{V}_{\mathrm{c}}-\mathrm{V}_{\mathrm{L}}\right)^2}\) \(=\sqrt{(40)^2+(80-40)^2}\)
\(\mathrm{e} =\sqrt{3200}\)
\(\therefore \mathrm{e} =40 \sqrt{2} \mathrm{~V}\)