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. 10V
B. 50V
C. 100V
D. 120V
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