This question was asked inSupervisor Instructor Electrical Part B Technical Paper 2026Question 102 of 120 published · Gujarat Subordinate Service Selection BoardOpen paper
Q102ModerateResonance

When an AC voltage is applied to a series RLC circuit operating at resonance, how does the circuit behave?

Answer & step-by-step solution
Correct answer: A. As a purely resistive circuit
Quick explanation

A — As a purely resistive circuit. At series resonance X_L = X_C and they cancel, so Z = R (minimum) and current is maximum and in phase with voltage.

Detailed solution (in the paper’s original language)

સમજૂતી

Series resonance પર inductive reactance અને capacitive reactance magnitude માં સમાન હોય છે અને એકબીજાને cancel કરે છે.

Net reactance zero હોવાથી circuit impedance માત્ર R રહે છે. તેથી circuit purely resistive વર્તે છે અને current maximum થાય છે.

મુખ્ય ખ્યાલ

Series resonance પર: X_L = X_C, તેથી Z = R.

સૂત્ર

fr = 1/(2π√LC); Zres = R.

પરીક્ષા મુદ્દો

Resonance પ્રશ્નમાં સૌ પહેલા X_L = X_C યાદ કરો.

ઝડપી ટ્રિક

Series resonance → minimum impedance, maximum current, unity PF.

બીજા વિકલ્પો ખોટા કેમ છે

Exact resonance પર reactances cancel થતાં inductive/capacitive behavior રહેતું નથી.

સામાન્ય ભૂલ

Series resonance ને parallel resonance સાથે ગૂંચવવું.

Solution diagram – When an AC voltage is applied to a series RLC circuit operating at resonance…
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