12th class (Fsc) Physics unit 5 MCQs
26. XL is low for low frequency f, but Xc is:
a. High
b. Zero
c. Same as HL
d. Low
27. The sum of positive and negative peak value is called:
a. Peak value
b. R.M.S value
c. Average value
d. P-P value
28. In A.C wave form, negative peak is obtained at the phase angle of:
a. 270o
b. 90o
c. 360o
d. 120o
29. At resonance frequency, the impedance of RLC series circuit is:
a. Zero
b. Maximum
c. Infinite
d. Minimum
30. Relation for resonance frequency of RLC series circuit is:
a. 1/2π√LC
b. 1/√2πLC
c. 1/√LC
d. 2π/√LC
31. Root mean square value of voltage is given by:
a. Vrms = Vo /√2
b. Vrms = 2Vo
c. Vrms = Vo / 2
d. Vrms = √2Vo
32. An A.C voltmeter reads 220V, its peak value will be:
a. 311.12 V
b. 225 V
c. 300 V
d. 340 V
33. In RLC series circuit the phase angle between Yc and Xc is:
a. tan-1 ꞷz/Rc
b. tan-1 ꞷc/R
c. πrad
d. tan-1 ꞷ/Rc
34. Inductive reactance of an inductor is:
a. XL = 2πfL
b. XL = πfL
c. XL = 2πL
d. XL = 4πfL
35. If Io the peak value of an A.C supply then its rms value will be given as Irms :
a. Io / 2
b. Io / √2
c. 2Io
d. √2Io
36. he output of an A.C generator at time is given by:
a. V=0
b. V= -Vo
c. V= 1
d. V= Vo
37. The power factor of RL-series circuit is:
a. Less than 1
b. 0
c. More than one
d. 1
38. In RLC series circuit at resonance the phase difference between capacitor and inductor reactances is:
a. 0o
b. 90o
c. 180o
d. 270o
39. The phase of A.C at positive peak from origin is:
a. π/4
b. 3π/2
c. π
d. π/2
40. One of the sources of an A.C voltage is:
a. UPS
b. Motor
c. Solar cell
d. Battery
41. The circuit which compares the two voltage is:
a. Comparator
b. LDR
c. Logic gate
d. Sensor
42. The basic circuit element in A.C circuit which controls current:
a. Inductor only
b. Resistor only
c. Capacitor only
d. All of these
43. The basic circuit elements in a D.C circuit is:
a. Capacitor
b. Resistor
c. Transistor
d. Inductor
44. In RLC series circuit, at resonance frequency Xc and XL are:
a. Differ by a phase π/2
b. In phase
c. At angle of 120o
d. Opposite in phase
45. The basic circuit element in a D.C circuit which controlled the current and voltage is:
a. Inductor
b. Capacitor
c. Transistor
d. Resistor
46. Phase difference between V and I of an A.C through resistor is:
a. 180o
b. Zero degree
c. 270o
d. 90o
47. In R-L-C circuit the energy is dissipated in:
a. R and C
b. R only
c. R, L and C
d. R and L
48. In three phase A.C generator the phase difference between each pair of coil is:
a. 90o
b. 45o
c. 120o
d. 60o
49. Resonating frequency of RLC series circuit of fr =………:
a. 1/ 2π√LC
b. 2π / √LC
c. 2P√LC
d. 1/ 2P √LC
50. In a A.C circuit with resistor only, the current and voltage have a phase angle of:
a. 0o
b. 180o
c. 6oo
d. 90o