AC CIRCUITS

What is the unit of susceptance? Mho Ohm Henry Farad

How the resonance frequency (fr) can be increased in A.C series circuit? Increasing the inductance value Reducing the capacitance value Increasing the capacitance value Increasing the resistance value

What is the main cause for below 0.5 lagging power factor in 3 phase system? Due to fluctuation of voltage True power due to resistive load Reactive power due to more inductive load Reactive power due to more capacitive load

What is the current in neutral conductor in 3 phase unbalanced load in star connected system? No current will flow The algebraic sum of current in 3 phases The algebraic sum of current in 2 phases only Lesser than the lowest current in any one of the phases

What will be the readings of two watt meters (W1& W2) in 3 phase power measurement, if the power factor is zero? W1 & W2 both are positive reading W1 is Positive and W2 is negative reading W1 is equal to W2 but with opposite signs Zero W1 is Positive reading, and W2 is negative reading

What is the maximum value of voltage for 240 volt RMS? 240V 415V 339.5V 376.8V

What is the formula for Reactive Power (Pr) in an AC circuit? Pr = VI Pr = √2 VI Pr = VI cos θ Pr = VI sin θ

What is the phase displacement in a single phase AC circuit? 90° 120° 180° 270°

What is the power factor in a 3 phase power measurement of two wattmeter showing equal readings? 0 1 0.5 0.8

Calculate the power factor of coil having resistance of 24Ω, draws the current of 5A, at 240V/ 50HZ AC supply. 0.8 0.6 0.5 0.3

Calculate the power factor of R.L.C circuit having resistance (R) = 15W, resultant reactance (X) = 20W connected across 240V /50Hz AC supply? 0.5 0.6 0.7 0.8

Calculate the value admittance (Y) of the RLC parallel circuit connected across 240 volts/50Hz AC supply and 8 Amp. Current is passed through it ? 3.33 Mhoi 0.33 Mho 0.033 Mho 0.0033

How the low power factor (P.F) can be improved in AC circuits? By connecting resistors in series By connecting capacitors in series By connecting inductors in series By connecting capacitors in parallel

What is the relation between the line current (IL) and phase current (IP) in delta connected system? IL = IP IL = 3 IP IL = √3 IP IL = IP / √3

What is the purpose of phase sequence meter? To control the speed of 3 phase motor To protect motor against short circuit fault To indicate the incorrect phase sequence of 3 phase To ensure the correct phase sequence of 3 phase system

Calculate the apparent power of a star connected 3 phase load, if it is connected across 3 phase 415 volt/50Hz supply at 0.8 p.f and the phase current is 10 Amps. 12. 45 KVA 57.50 KVA 3.320 KVA 7.188 KVA

What is the P.F if one of the wattmeters reading is zero and the other reads total power in 2 wattmeter method of 3 phase power measurement? 0.5 0 1 Below 0.5

What is the formula for form factor (Kf)? Kf= Average value / RMS value Kf= RMS value / Average value Kf= Maximum value / Average value Kf= RMS value / Maximum value

Which electrical term is defined as the total opposition to current in AC parallel circuit? Resistance Impedance Admittance Susceptance

Which AC circuit contains the phase relation between voltage (V) and current (I)? Pure resistive circuit Resistance and inductance circuit Resistance and capacitance circuit Resistance, inductance and capacitance circuit

In a 3 phase system, if the active power is 4kw and the apparent power is 5 KVA, calculate the reactive power? 1 KVAR 2 KVAR 3 KVAR 4 KVAR

In which condition resonance will occur in an RLC series circuit? Inductive reactance (XL) is zero Inductive reactance (XL) is equal to capacitive reactance (XC) Inductive reactance (XL) is greater than capacitive reactance (XC) Inductive reactance (XL) is less than capacitive reactance (XC)

How will you obtain positive reading in the wattmeter reads negative reading during 3- phase two wattmeter method? By interchanging the connections of input terminals By disconnecting the connection of current coil in meter By reversing the connection of pressure coil in meter By reversing the connection of pressure coil in meter

What is the form factor (Kf) for sinusoidal AC? 1 1.11 2.22 4.44

What is the reciprocal of inductance in AC parallel circuit? Reactance Admittance Conductance Susceptance

Calculate the total power by two wattmeter(W1 & W2) method, if one of the wattmeter (W2)reading is taken after reversing. W1 x 2 W1 only W1 - W2 W1 + W2

Which 3 phase system, the artificial neutral is required to measure the phase voltage? 3 wire star connected system 4 wire star connected system 3 wire delta connected system 4 wire delta connected system

What is the line voltage in 3 phase system if the phase voltage is 240V? 380 Volt 400 Volt 415 Volt 440 Volt

What is the power factor if one of the wattmeter gives negative reading in two wattmeter method of 3 phase power measurement? 0 0.5 1 Less than 0.5

What is the phase displacement between phases in a 3-phase circuit? 90° 120° 180° 360°

Which condition is called as resonance RLC circuit? XL > XC XC > XL XL = XC R < XL