Answer: E. 120.Total harmonic distortion is defined according to the formula:

 

120. Total harmonic distortion is defined according to the formula:

A)(√Y₁²+Y₂²+Y₃²+…+Yn²)/│Y1│

B) │Y1│/(√Y₁²+Y₂²+Y₃²+…+Yn²)

C) (√Y₂²+Y₃²+…+Yn²)/│Y1│;

D) │Y1│/(√Y₂²+Y₃²+…+Yn²)

E) │Y1│*(√Y₂²+Y₃²+…+Yn²)

Answer: C

121. Define Thevenin impedance for the circuit in fig.15. Z_T(s)=____ Fig.15

A) R/(RCs+1) B) RC/(RCs+1) C) R/(Rs+1)

D) Rs/(RCs+1) E) Rs/(RC+1)

Solution:

Z_R(s)=R

Z_C(s)=1/Cs

Z_T=(R/Cs)/ (1/Cs+R)=R/(RCs+1)

Answer: A

122. Define the current of short circuit I_SC(s) for the circuit in fig.16.

 

 

fig.16

A)I_SC(s) = V_S/s

B) I_SC(s) = RV_S/s

C) I_SC(s) = V_S/Rs

D) I_SC(s) = V_S/RCs

E) I_SC(s) = V_S/RCs+1

Solution:

Ј{V(t)}= V_S/s

I_SC(s) = V_S/Rs

Answer: C

 

123. Which of the elements are non-linear?

A) resistor

B) inductor

C) diode

D) capacitor

E) potentiometer

Answer: C

 

124. In series RLC circuit oscillations takes place during the transient when we have got_____ response.

A)overdamped

B) critically damped

C) underdamped
D) overdamped or underdamped

E) there are no oscillations at all

Answer: C

 

125. The unit of inductance is

A).C

B)F

C).H

D)V*s/A

E) answers C and D are both correct

Answer: E

 

126. Total harmonic distortion for the pure sinusoid is equal to

A) 1 B) 0 C) from 0 to 1 D) more than 1 E) may be any value

Answer: B

 

127. For RL circuit when frequency increases 2 times the impedance of the circuit _______.

A)increases 2 times

B) decreases 2 time

C) increases less than 2 times

D) decreases more than 2 times

E) decreases less than 2 times

Solution:Z₁=ÖR²+(wL)², Z₂=ÖR²+(2wL)², so if R=2Ω, wL=2Ω, 2wL=4Ω, Z₁=Ö2²+2²=Ö8 Ω

Z₂=Ö2²+4²=Ö20 Ω. Z₂/Z₁=Ö20/Ö8=1.58

Answer: C

 

128. If a waveform has a half-wave symmetry the Fourier series consist of _______ harmonics.

A) sine

B) cosine

C) sine and cosine odd

D) sine and cosine even

E) sine odd and cosine even