21. A resistance of 7 ohms is connected in series with an inductance of 31.8mH. The circuit is connected to an x V 50Hz sinusoidal supply. The current in the circuit is 8.2A. Calculate the value of x.
A. 10 V
B. 50 V
C. 100 V
D. 120 V
22. Which among the following is the correct expression for φ?
A. φ = tan-1 (XL/R)
B. φ = tan-1 (R/XL)
C. φ = tan-1 (XL × R)
D. φ = cos-1 (XL/R)
23. For an RL circuit, the phase angle is always ________
A. Positive
B. Negative
C. 0
D. 90
24. What is φ in terms of voltage?
A. φ = cos-1V/VR
B. φ = cos-1V × VR
C. φ = cos-1VR/V
D. φ = tan-1V/VR
25. What is sinϕ from the impedance triangle?
A. XL/R
B. XL/Z
C. R/Z
D. Z/R
26. What is the resonance frequency of ac circuit?
A. 1/√LC
B. √(L/C.
C. √LC
D. LC
27. What is impedance at resonance?
A. maximum
B. minimum
C. zero
D. cannot be determined
28. What is the value of impedance at resonance?
A. XL
B. XC
C. R
D. 0
29. What is φ in terms of voltage?
A. φ = cos-1V/VR
B. φ = cos-1V × VR
C. φ = cos-1VR/V
D. φ = tan-1V/VR
30. What is tanϕ for the RC circuit?
A. XC/R
B. XL/R
C. R/Z
D. Z/R