Electrical Engineering GATE 2015 Set-2 Questions with Answer

Ques 27 Electrical Machines

With an armature voltage of 100 V and rated field winding voltage, the speed of a separately excited DC motor driving a fan is 1000 rpm, and its armature current is 10 A. The armature resistance is 1 Ω. The load torque of the fan load is proportional to the square of the rotor speed. Neglecting rotational losses, the value of the armature voltage (in Volt) which will reduce the rotor speed to 500 rpm is ________.

Ques 28 Electrical Machines

A three-phase, 11 kV, 50 Hz, 2 pole, star connected, cylindrical rotor synchronous motor is connected to an 11 kV, 50 Hz source. Its synchronous reactance is 50 Ω per phase, and its stator resistance is negligible. The motor has a constant field excitation. At a particular load torque, its stator current is 100 A at unity power factor. If the load torque is increased so that the stator current is 120 A, then the load angle (in degrees) at this load is ________.

Ques 29 Electrical Machines

A 220 V, 3-phase, 4-pole, 50 Hz inductor motor of wound rotor type is supplied at rated voltage and frequency. The stator resistance, magnetizing reactance, and core loss are negligible. The maximum torque produced by the rotor is 225% of full load torque and it occurs at 15% slip. The actual rotor resistance is 0.03 Ω/phase. The value of external resistance (in Ohm) which must be inserted in a rotor phase if the maximum torque is to occur at start is ________.

Ques 30 Electrical Machines

Two three-phase transformers are realized using single-phase transformers as shown in the figure. The phase difference (in degree) between voltages V₁ and V₂ is ________.

Ques 31 Electrical Measurements

The coils of a wattmeter have resistances 0.01Ω and 1000Ω; their inductances may be neglected. The wattmeter is connected as shown in the figure, to measure the power consumed by a load, which draws 25A at power factor 0.8. The voltage across the load terminals is 30V. The percentage error on the wattmeter reading is ________.

Ques 32 Electrical Measurements

Match the following.

Ques 33 Electrical Measurements

A 3-phase balanced load which has a power factor of 0.707 is connected to a balanced supply. The power consumed by the load is 5 kW. The power is measured by the two-wattmeter method. The readings of the two wattmeters are

Ques 34 Electrical Measurements

A capacitive voltage divider is used to measure the bus voltage V_bus in a high-voltage 50 Hz AC system as shown in the figure. The measurement capacitors C₁ and C₂ have tolerances of ±10% on their nominal capacitance values. If the bus voltage V_bus is 100 kV rms, the maximum rms output voltage V_out (in kV), considering the capacitor tolerances, is ________.

Ques 35 Electromagnetics

Two semi-infinite conducting sheets are placed at right angles to each other as shown in the figure. A point charge of +Q is placed at a distance of d from both sheets. The net force on the charge is (Q²)/(4πε₀) * (K/d²), where K is given by

Ques 36 Electromagnetics

Two semi-infinite dielectric regions are separated by a plane boundary at y=0. The dielectric constants of region 1 (y<0) and region 2 (y>0) are 2 and 5, respectively. Region 1 has uniform electric field E = 3â_x + 4â_y + 2â_z, where â_x, â_y, and â_z are unit vectors along the x, y and z axes, respectively. The electric field in region 2 is

Ques 37 Electromagnetics

A circular turn of radius 1 m revolves at 60 rpm about its diameter aligned with the x-axis as shown in the figure. The value of μ₀ is 4πx10^-7 in SI unit. If a uniform magnetic field intensity H⃗ = 10⁷ẑ A/m is applied, then the peak value of the induced voltage, V_turn (in Volts), is ________.

Ques 38 Engineering Mathematics

The volume enclosed by the surface f(x,y) = e^x over the triangle bounded by the lines x=y; x=0; y=1 in the xy plane is ________.

Ques 39 Engineering Mathematics

Two coins R and S are tossed. The 4 joint events H_RH_S, T_RT_S, H_RT_S, T_RH_S have probabilities 0.28, 0.18, 0.30, 0.24, respectively, where H represents head and T represents tail. Which one of the following is TRUE?