ALTERNATING CURRENT ASSERTION and REASON
Each question has 4 choices (A), (B), (C) and (D) out of which ONLY ONE is correct. So select the correct
choice : Choices are :
(A) ASSERTION is True, REASON is True; & REASON is a correct explanation for ASSERTION .
(B) ASSERTION is True, REASON is True; & REASON is NOT a correct explanation for ASSERTION
(C) ASSERTION is True, but REASON is false.
(D) ASSERTION is false, and REASON is also false
1. ASSERTION: The alternating current cannot be used to conduct electrolysis.
REASON: The ions due to their inertia, cannot follow the changing electric field.
2. ASSERTION: In a series LCR circuit at resonance, the voltage across the capacitor or inductor may be
more than the applied voltage.
REASON: At resonance in a series LCR circuit, the voltages across inductor and capacitor are out of
phase.
3. ASSERTION: By only knowing the power factor for a given LCR circuit it is not possible to tell
whether the applied alternating emf leads or lags the current.
REASON: cos Ɵ= cos (–Ɵ)
4. ASSERTION: In the purely resistive element of a series LCR, AC circuit the maximum value of rms
current increases with increase in the angular frequency of the applied emf.
REASON: I max = E max / Z where Z2 = (ω2L2) – (1 / ω2C2) where Imax is the peak current in a cycle.
5. ASSERTION: AC source is connected across a circuit. Average power dissipated in circuit is P. The
power is dissipate only across resistance.
REASON: Inductor and capacitor will not consume any average power in AC circuit.
6. ASSERTION: In series RLC circuit potential drop across inductive reactance will be same as
capacitive reactance at resonance.
REASON: At frequency less than resonance frequency for series RLC nature of circuit will be capacitive,
and for the frequency more than resonance nature of overall circuit will be inductive.
7. ASSERTION: For series RLC network, power factor of circuit in region (1) where (ω > ω 0) is positive
and in region (2) where (ω < ω0) is negative.( here ω0 is resonance frequency)
REASON: Overall nature of circuit in region (1) is capacitive while in region (2) is inductive.
8. ASSERTION: In a series LCR circuit, at resonance condition power consumed by circuit is maximum.
REASON: At resonance condition effective resistance of circuit is maximum.
9. ASSERTION: In series L–R circuit voltage leads the current.
REASON: In series R–C circuit current leads the voltage.
10. ASSERTION: Average value of a.c. over a complete cycle is always zero.
REASON: Average value of a.c. is always non zero over half cycle.
11. ASSERTION: In series LCR circuit resonance can take place.
REASON: Resonance takes if inductance and capacitive reactance are eq
12. ASSERTION: KVL can not be used directly in AC circuit .
REASON: in ac circuits Iinstantaneous = Iactual
13. ASSERTION: AC generators are based upon EMI principle.
REASON: Resistance offered by capacitor for alternating current is zero.
14. ASSERTION: For sinusoidal a.c. I instantaneous = I0 sin ωt amp
Rms current can not be 9 amp .
REASON: The r.m.s. value of alternating current is defined as the square root of the average of square of
I instantaneous during a complete cycle.
15. ASSERTION: Rate of heat generated when resistance is connected with AC source depends on time.
REASON: RMS voltage may be greater than maximum AC voltage.
16. ASSERTION: An inductor, capacitor and resistance connected in series. The combination is
connected across AC source. Then Peak current through each remains same.
REASON: Average power delivered by source is equal to average power developed across resistance.
17. ASSERTION: In alternating current direction of motion of free electrons changes periodically.
REASON: Alternating current changes its direction not magnitude after a certain time interval.
18. ASSERTION: When frequency is greater than resonance frequency in a series LCR circuit, Resultant
voltage will lead the current.
REASON: it will be an inductive circuit.
19. ASSERTION: When capacitive reactance is smaller than the inductive reactance in LCR circuit, e.m.f.
leads the current.
REASON: The phase angle is the angle between the alternating e.m.f. and alternating current of the
circuit.
20. ASSERTION: An alternating current shows magnetic effect.
REASON: Alternating current varies with time.
