# Top 50 Electrical Engineering Interview Questions 1. What will happen to torque if the DC series motor is connected to AC supply?
2. An 8 pole 3 phase alternator running at 1500rpm supplies power to 6 pole 3 phase induction motor with rotor current frequency of 1Hz. What is the speed?
3. A 3phase 100MVA 25kV generator has reactance of 0.032ohm per phase. Find the pu (Per Unit) at 50MVA and 10kV?
4. The slip test yielded the maximum parameters of 110V and 14A, and minimum parameters of 94V and 8A. Find Xd (Direct Axis Reactance) and Xq (quadrature axis reactance)?
5. A 30kVA, 3000/300V transformers has leakage impedance of 8%. What is the voltage required on low voltage side to circulate full load current in high voltage side during short circuit?
6. At full load, the core loss is 100W and copper loss is 200W. What is the loss at 25% of the load?
7. Two 100kV/10kV transformers with rating 1200kVA and 700kvA are in parallel sharing a load of 1600kVA. The reactance as seen from secondary of the transformers are 0.02ohms and 0.03 ohms. Find the load sharing?
8. A 3-phase transmission line spaced as equilateral triangle has the sides of 5 meters and the radius of each conductor is 2cm. Calculate the inductance of line per phase per km.
9. A cable has capacitance of 2uF per km and inductance of 0.022mH/km. Find the surge impedance of the cable.
10. A circuit has v = Vsin(ωt+30) and i = Isin(ωt-30). What are the real, reactive and apparent powers in pu?
11. A 200kV surge travels from an overhead line to the cable. The surge impedance of line is 200ohms and that of cable is 25ohms. What is the surge transmitted to the cable from line?
12. The Y bus of a 1000 bus system is 95% sparse. Find the total number of transmission lines?
13. A single phase full bridge has freewheeling diode feeding inductive load. The load resistance is 10ohms. The load inductance is large to provide ripple free dc currents. The input to converter is 200V, 60Hz. Find the average diode current for the firing angle of 60 degrees?
14. The magnetic flux of a 300 turn coil is given by t4+4t3+3t2+2t+500 milli webers. Find the induced emf at t = 3s?
15. A free space has H(z,t) = 0.2sin (5×107t-az)Tx. Find the expression of E?
16. A copper wire has a conduction current of 2A at 60Hz. If the conductivity is 5.8 mho/m, find the displacement current?
17. The impulse response of LTI system is 7u (t). If the input is e-t then find output?
18. Three currents entering the node as i1 = 5cos (10t+30), i2 = 5cos(10t-30). Find i3.
19. In two wattmeter method, one of the wattmeter reads 0. Find the power factor of the load?
20. An energy meter has a meter constant of 1150 rev per kWhr. It makes 8 revolutions in a minute. Find the power of the load?
21. Piezoelectric transducer of 1cm possessing the g-coefficient of 6mV/kg/sqm is subjected to a pressure for 25minutes with a value of 8kg/sqm. Find the voltage developed by the transducer?
22. The impedance of a simple RLC parallel network is given by Z(s) = 6s/(s2+0.8s+81). Find the value of R, L and C?
23. A step function of 2A is applied to circuit having the driving point impedance as Z(s) = (s+4)/(s+5)2. Find the initial and final values of voltages?
24. A slab of dielectric has a dielectric constant of 7. It is placed normal to the uniform field possessing the flux density of 4 C/sqm. Find the polarization if the slab was uniformly polarized?
25. An oscilloscope with XY settings of 0.5ms/cm and 100mV/cm displays a sine wave of 250mV rms and frequency of 200Hz. The size of screen is 10cm x 8cm. Describe the output shown in screen?
26. For a Q meter, the first resonance occurred at y Hz with C1 = 700pF and the second resonance occurred at 3y Hz at C2 = 50pF. Find the self capacitance of the coil?
27. A strain gauge has a resistance of 300ohms. It undergoes a change of 0.08ohms when tested with a load. The strain was measured to be 1.1 x 10-4. Find the gauge factor?
28. The impulsive response of a second order system is given by .4e-.06tsin (0.8t). Find the natural frequency of oscillation and the damping ratio?
29. The second order of the system was given as M(jw) = 100/(100-w2+10sqrt(2)jw. Find the peak magnitude?
30. A 120V DC motor has the back emf of 105V and armature resistance of 0.5ohms. Find the current drawn by the DC motor.
31. An 8 pole induction machine runs at the speed of 720rpm. Find the frequency of the induced emf in rotor if the supply frequency has 50Hz.
32. A current of 2A flows into a coil consisting of 100turns thus creating a core flux of 3mWb. Find the energy stored in the magnetic field.
33. A generating station has load factor of 70%, maximum demand of 40MW and plant capacity factor of 56%. Find the reserve capacity for the generating station.
34. A 120km, 132kV long transmission line has a load of 180MVA with the loss of 20MW on the line. Find the resistance of the line
35. The zero sequence current for a line to ground fault in a generator is j2.2pu. Find the current flowing through the neutral during fault?
36. The open loop gain of op amp is 340. The noise level without feedback in the output is 80mV. If a feedback of 1/50 is used, find the noise level in the output?
37. An operational amplifier has a differential gain of 10000 and CMRR of 10. If the input voltages are 115uV and 85uV, find the output voltage?
38. An ideal chopper of 1 kHz supplies load with resistance 6ohms and inductance of 3mH from a 50V battery. The ON/OFF ratio is 4/1. Find the average load voltage?
39. Find the minimum and maximum firing angle for a single phase, half wave controlled rectifier having the source of 200V rms and the back emf of 40V?
40. A single phase half bridge inverter feeds a load of 1.8ohms. The input voltage is 50V. Find the RMS output voltage at fundamental frequency?
41. A boost converter has input of 5V and output of 15V. Find the duty cycle?
42. Find the force per unit length for a current carrying conductor of 7A in positive Z direction and placed in magnetic field of B= (5ax + 12ay)?
43. Derive an approximate value of capacitance between two spheres whose separation is much larger than their radii?
44. The intrinsic impedance in a lossless medium is 80 x pi. The relative permeability is 1. Find the value of relative permittivity?
45. A lossless transmission line of 60cm has L = 9uH/m, C = 25pF/m. Find the electrical length if it is operated at 40MHz.
46. A dielectric material has a loss tangent of 0.003. The real part of dielectric constant is 5. Find the complex dielectric constant.
47. Transfer function is Z(s) = s/(s+6). A current of i(t) = 4u(t) was given. Find v(t)?
48. A balanced delta has impedance of 12<40 ohms per phase. Find its equivalent star?
49. In series RLC circuit, the voltage across R and L is 30V. Voltage across R, L and C is 22.5V. Voltage across L and C is 13.5V. Find the voltage across Capacitor.
50. A 0 to 400V voltmeter has accuracy of 2% of full scale. The voltage measured now using this instrument is 70V. Find the limiting error.