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A 50 Hz voltage is measured with a moving iron voltmeter and a rectifier type AC voltmeter connected in parallel. If the meter readings are Va and Vb respectively. Then the form factor may be estimated as?(a) \(\frac{V_a}{V_b} \)(b) \(\frac{1.11V_a}{V_b}\)(c) \(\frac{\sqrt{2} V_a}{V_b}\)(d) \(\frac{πV_a}{V_b}\)I have been asked this question in an online interview.My question comes from Problems of Series Resonance Involving Quality Factor in chapter Resonance & Magnetically Coupled Circuit of Network Theory |
Answer» RIGHT choice is (b) \(\frac{1.11V_a}{V_b}\) Explanation: Form FACTOR of the wave = \(\frac{RMS \,value}{Mean \,value}\) MOVING iron instrument will show rms value. Rectifier voltmeter is calibrated to READ rms value of sinusoidal voltage that is, with form factor of 1.11. ∴ Mean value of the applied voltage = \(\frac{V_b}{1.11}\) ∴ Form factor = \(\frac{V_a}{V_b/1.11} = \frac{1.11V_a}{V_b}\). |
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