CBSE Class 12-science Answered
The given circuit diagram shows a series LCR circuit connected to a variable frequency 230 V source:
(a) Determine the source frequency, which drives the circuit in resonance.
(b) Obtain the impedance of the circuit and the amplitude of current at the resonating frequency.
(c) Determine the rms potential drops across the three elements of the circuit.
(d) How do you explain the observation that the algebraic sum of the voltage of the three elements obtained in (c) is greater than the supplied voltage?
OR
The primary coil of an ideal step-up transformer has 100 turns and the transformation ratio is also 100. The input voltage and the power are 220 V and 1100 W respectively. Calculate:
(i) number of turns in the secondary
(ii) the current in the primary
(iii) voltage across the secondary
(iv) the current in the secondary
(v) power in the secondary
(a) Determine the source frequency, which drives the circuit in resonance.
(b) Obtain the impedance of the circuit and the amplitude of current at the resonating frequency.
(c) Determine the rms potential drops across the three elements of the circuit.
(d) How do you explain the observation that the algebraic sum of the voltage of the three elements obtained in (c) is greater than the supplied voltage?
OR
The primary coil of an ideal step-up transformer has 100 turns and the transformation ratio is also 100. The input voltage and the power are 220 V and 1100 W respectively. Calculate:
(i) number of turns in the secondary
(ii) the current in the primary
(iii) voltage across the secondary
(iv) the current in the secondary
(v) power in the secondary
Asked by Topperlearning User | 22 Jun, 2015, 12:45: PM
Expert Answer
(b) At resonance, Z = R = 40 Ω
Current amplitude,
(c)
The algebraic sum of the three voltages is more than the source voltage of 230V. These voltages are not in the same phase and cannot be added like ordinary numbers. The voltage across L and C are out of phase and get added to zero. So,
= Applied rms voltage.
OR
Given Np = 100,Transformation ratio = 100,
Vp = 220 V,PP = 1100W
(i) Ns= Transformation ratio 
Np = 100 100 = 10000
(ii)
(iii) Vs = Transformation ratio VP = 100 220 = 22000 V
(iv)
(v) For an ideal transformer,
PS= PP = 1100W
Answered by | 22 Jun, 2015, 02:45: PM
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