ME or MEng Master of Engineering Master of Electrical Engineering 2

Question 1

In a three-phase induction motor, if the rotor resistance is doubled while the load torque remains constant, what primarily happens to the slip?

Accepted Answer

Slip doubles

Answer

In the equivalent circuit model, slip is proportional to rotor resistance for a given torque, so doubling rotor resistance doubles the slip.

Question 2

Which modulation scheme achieves the highest spectral efficiency in a bandwidth-limited wireless channel?

Accepted Answer

256-QAM

Answer

256-QAM encodes 8 bits per symbol, giving the highest spectral efficiency (bits/s/Hz) among these options.

Question 3

For a buck-boost DC-DC converter operating in continuous conduction mode, what is the voltage conversion ratio M = V_out/V_in as a function of duty cycle D?

Accepted Answer

-D/(1-D)

Answer

The buck-boost converter inverts polarity, giving M = -D/(1-D), where the negative sign indicates output polarity reversal.

Question 4

In CMOS logic design, which phenomenon causes dynamic power dissipation?

Accepted Answer

Charging and discharging of load capacitances

Answer

Dynamic power P = α·C·V²·f arises from charging and discharging load capacitances at each switching event.

Question 5

A transmission line has a characteristic impedance Z₀ = 50 Ω and is terminated with Z_L = 100 Ω. What is the reflection coefficient Γ?

Accepted Answer

0.33

Answer

Γ = (Z_L - Z₀)/(Z_L + Z₀) = (100-50)/(100+50) = 50/150 = 1/3 ≈ 0.33.

ME or MEng Master of Engineering Practice Test

ME or MEng Master of Engineering Practice Test

ME or MEng Master of Engineering Master of Electrical Engineering 2