Q.1. The unit of reactance is
(A) Ohm
(B) Farad
(C) Ampere
(D) Mho
Ans :- (A)
Q.2. Impedance of L-R circuit is
(A) R+ωL
(B) R²+ω²L²
(C) √R+ωL
(D) √R²+ω²L²
Ans:- (D)
Q.3. If φ is the phase difference between a.c. current and e.m.f then the value of power factor is
(A) tan φ
(B) cos²φ
(c) sinφ
(D) cosφ
Ans:- (D)
Q.4. The power factor of L-R circuit is
(A) R+ ωL
(B) R / √R²+L²ω
(C) R+ √R²+ω² L²
(D) ωL/R
Ans:- (B)
Q.5. The equation of an ac is represented by 1=0.6 sin 100πt the frequency of ac is
(A) 50π
(B) 50
(C) 100π
(D) 100
Ans:- (B)
Q.6. What is SI unit of alternating current
(A) Coulomb
(B) Coulomb-second
(C) Ampere
(D) Henry
Ans:- (C)
Q.7. Unit of inductive reactance (Xl) is
(A) Ohm
(B) Ohm- Meter
(C) Ampere
(D) Volt
Ans:- (A)
Q.8. Unit of impedance (Z) is
(A) Volt
(B) Henry
(C)Watt
(D) Ohm
Aans:- (D)
Q.9. Thevalue of V in the =circuit shown is
(A) 20V
(B) Zero
(C) Can not be soid
(D) none of these
Ans:- (A)
Q.10. A Choke coil is
(A) An inductor
(B) A resistor
(C) A capacitor
(D) None of these
Ans:- (A)
Q.11. If the phase difference between the current and voltage is negative it means that the current
(A) Leads the voltage
(B) Lags the voltage
(C) Both ‘A’ and ‘B’
(D) None of these
Ans:- (A)
Q.12. If a coil is open then inducatnce L and R(Resistance) becomes
(A) Infinity and Zero
(B) Zero and infinity
(C) Infinity and infinity
(D) Zero and Zero
Ans:- (B)
Q.13. For high frequency capacitor offers
(A) More reactance
(B) Zero reactance
(C) Less reactance
(D) Noneof these
Ans:- (C)
Q.14. Current in a circuit is wattless if
(A) inductance in the circuit is zero
(B) Resistance in the circuit is zero
(C) Current is alternating
(D) Resistance and inductance both and zero
Ans:-(B)
Q.15. How can we improve the φ-factor of a series resonant circuit
(A) By decreasing ‘R’
(B) By decreasing capacitance
(C) By increasing indvctance
(D) All of above
Ans:-(D)
Q.16. Alternating current can be produced by
(A) A transformer
(B) An electric motor
(C) Dynamo
(D) None od these
Ans:- (C)
Q.17. The frequency of alternating current mains in india is
(A) 25Hℤ
(B) 50HZ
(C) 30HZ
(D) 60HZ
Ans:-(B)
Q.18. Alternating current shows
(A) Chemical effect
(B) Magnetic effect
(C) Heating effect
(D) None of these
Ans:-(C)
Q.19. Hot wire ammeters are used for measueing
(A) D.C only
(B) A.C only
(C) Both a.c and d.c
(D) None of these
Ans:-(C)
Q.20. Alernating current ismeasured by
(A) An ammeter
(B) Heating effect of current
(C) Thermopile
(D) None of these
Ans:- (B)
Q.21. How wire instruments measure
(A) Peak value of a.c
(B) Average value of a.c
(C) Rms value of a.c
(D) None of these
Ans:-(C)
Q.22. The power factor of purely resistive a.c circuit is
(A) Zero
(B) One
(C) infinite
(D) O.S
Ans:-(B)
Q.23.The power factor is one for
(A) pure resistor only
(B) Pure inductor only
(C) Pure Capacitor Only
(D) None of these
Ans:- (A)
Q.24. A choke coil has
(A) High inductance and high resistance
(B) High inductance and low resistance
(C) Low inductance and low resistance
(D) None of these
Ans:-(B)
Q.25. Alternating current of 3A is the same as
(A) 3 coulomb/Second
(B) 3ohm/meter
(C) 3 joule/coulomb
(D) None of these
Ans:- (A)
Q.26. The choke coil is used to control
(A) A.c
(B) D.c
(C) both a.c and D.c
(D) None of these
Ans:- (A)
Q.27. The ratio of peak value and r.m.s value of ac is
(A) 2
(B) √2
(C) 1/√2
(D) 1/2
Ans:-(B)
Q.28. An a.c circuit contains capacitor the resistance offered by the capacitor is increased
(A) By decreasing the angular frequency
(B) By decreasing the capacitance of capacitor
(C) both ‘A’ and ‘B’ are correct
(D) Non of these
Ans:-(C)
Q.29. An Lc circuit cannot produce oscillations when
(A) Capacitance is large
(B)Inductance is large
(C) resistance is large
(D) none of these
Ans:- (C)
Q.30. In a LR circuit the correct rises to final value slowly when
(A) Lis small
(B) Lis large
(C) Lis zero
(D) none of these
Ans:- (B)
Q.31. The rms voltage of an a.c. is 220v. the peak value is
(A) 220√2v
(B) √2/220v
(C) 220v
(D) 220√2v
Ans:- (D)
Q.32. The maximum value of the power factor is
(A) 1
(B) 2
(C) Infinity
(D) 100
Ans:- (A)
Q.33. The power factor of an a.c. circuit is o.s. what will be the phase difference between voltage and current in this circuit
(A) 9⁰
(B) 180⁰
(C) 60⁰
(D) 0⁰
Ans:- (c)
Q.34. The reading of a hot wire voltmeter is 220 volt the peak value of A.c. voltage
(A) 311 volt
(B) 320 volt
(C) 211 volt
(D) 0 volt
Ans:- (A)
Q.35. A choke coil is perferred to a rheosantin an a.c. circuit as it
(A) increases current
(B) increases power
(C) Consumes almost zero power
(D) none of these
Ans:- (C)
Q.36. For high frequency indutet offers
(A) more reactance
(B) Zero reactance
(C) Less reactance
(D) none of these
Ans:- (A)
Q.37. Transformer are used in
(A) direct current
(B) Alternating current
(C) both d.c.and a.c
(D) none of these
Ans:- (B)
Q.38. Transformer is used to convert
(A) a.c. into d.c.
(B) d.c. into a.c.
(C) low voltage to highand vice versa
(D) none of these
Ans:- (C)
Q.39. An a.c. circuit contains inductor ,the inductive reactance is increased
(A) By increasing the angular frequency
(B) By incrreasing inductance
(C) Both ‘A’and ‘B’ are correct
(D) none of these
Ans:-(C)