A.C. CIRCUITS (SERIES AND PARALLEL)

The phase angle for a series RC circuit may be computed as the angle between the ___ and the ___ phasors. A. resistance, impedance B. resistance, reactance C. resistance, capacitance D. impedance, reactance

A. resistance, impedance

At a frequency less than the resonant frequency A. series circuit is capacitive and parallel circuit is inductive B. series circuit is inductive and parallel circuit is capacitive C. both circuits are inductive D. both circuits are capacitive

A. series circuit is capacitive and parallel circuit is inductive

In resonant circuits, the power factor at resonance is A. zero B. 1 C. 0.5 D. 0.707

B. 1

The frequency at which maximum voltage occurs across the capacitance in RLC series circuit is A. 1/2π√LC B. 1/2π√(1/LC - R^2/2L^2) C. 1/2π√LC (√R^2/2L^2) D. 1/2π√(1/LC^2 - R^2/2L)

B. 1/2π√(1/LC - R^2/2L^2)

In a series RC circuit, the voltage across the capacitor and the resistor are 60 V and 80 V respectively. The input voltage should be A. 70∠45° B. 100∠-37° C. 105∠-42° D. 108∠-60°

B. 100∠-37°

The phase angle for a series RC circuit is defined as the angle between the ___ and the ___ phasors. A. current, resistance voltage B. current, total voltage C. resistance voltage, capacitor voltage D. R, XC

B. current, total voltage

To a highly inductive circuit, a small capacitance is added in series. The angle between voltage and current will A. increase B. decrease C. remain nearly the same D. become indeterminate

B. decrease

The resistance phasor for a series RC circuit points out to the right. The capacitive reactance phasor points ___ while the diagonal of the rectangle having there two phasors as sides represents the ___. A. up, impedance B. down, impedance C. left, current D. up, total voltage

B. down, impedance

The currents flowing in L and C at parallel resonance are A. zero B. equal C. infinite D. different

B. equal

A series resonant circuit is capacitive at f = 100 Hz. The circuit will be inductive somewhere at A. f < 100 Hz B. f > 100 Hz C. f = 100 Hz by increasing the value of the resistance D. f = 0

B. f > 100 Hz

The voltage across a capacitor ___ the current through it by ___. A. lags, 45° B. lags, 90° C. leads, 0° D. leads, 90°

B. lags, 90°

In a series RLC circuit, the impedance at resonance is A. maximum B. minimum C. infinity D. zero

B. minimum

The phase angle of a series RL circuit is the angle between the ___ phasor and the ___ phasor. A. resistance, inductive reactance B. resistance, impedance C. inductive reactance, impedance D. inductance, impedance

B. resistance, impedance

If f1 and f2 are half power frequencies and f0 be resonance frequency, the selectivity of RLC series circuit is given by A. (f2-f0)/(f1-f0) B. (f2-f1)/f0 C. (f2-f1)/(f1-f0) D. (f2-f1)/2f0

C. (f2-f1)/(f1-f0)

The frequency at which maximum voltage occurs across the inductance in RLC series circuit is A. 1/2π√LC B. 1/2π√(LC-R^2) C. 1/2π√(LC-(C^2 R^2)/2) D. 1/2π√((LC-C^2 R^2)/2)

C. 1/2π√(LC-(C^2 R^2)/2)

There will ___ be a frequency, called the ___ frequency at which ___. A. sometimes, natural; XL = XC B. always, natural; R = 0 C. always, resonant; XL = XC D. sometimes, resonant; R = 0

C. always, resonant; XL = XC

If the resistance in a series RC circuit is increased the magnitude of the phase angle A. increases B. remains the same C. decreases D. changes in an indeterminate manner

C. decreases

In a series RL circuit phasor diagram, total voltage may be represented by the ___ phasor and the resistor voltage may be represented by the ___ phasor. A. current, voltage B. current resistance, current C. impedance, resistance D. impedance, inductance

C. impedance, resistance

A(n) ___ stores and returns energy to a circuit while a(n) ___ dissipates energy. A. resistor, impedance B. resistor, inductor C. inductor, resistor D. inductor, reactance

C. inductor, resistor

In a series RL circuit, the inductor current ___ the resistor current. A. lags B. leads C. is equal to D. is negative of

C. is equal to

In a series RC circuit, the current ___ the total voltage by an angle ___. A. lags, of 45° B. lags, of 0° C. leads, between 0° and 90° D. leads, of 90°

C. leads, between 0° and 90°

The total voltage in a series RL circuit ___ the current by an angle ___. A. lags, of 90° B. lags, between 0° and 90° C. leads, between 0° and 90° D. leads, between 90° and 180°

C. leads, between 0° and 90°

Which of the following statements is true for series RLC circuit tuned at resonant frequency? A. the voltage across C > applied voltage B. the voltage across L > applied voltage C. the voltage across L and C > the applied voltage D. the voltage across both L and C < the applied voltage

C. the voltage across L and C > the applied voltage

The formula for the resonant frequency is f = A. √LC B. 1/√LC C. 2π√LC D. 1/2π√LC

D. 1/2π√LC

The net reactance in a series RLC circuit is A. XL B. XC C. XC +XL D. XL - XC

D. XL - XC

The value of current at resonance in a series RLC circuit is affected by the value of A. R B. C C. L D. all of these

D. all of these

The transient currents are due to A. voltage applied to circuit B. resistance of the circuit C. impedance of the circuit D. changes in stored energy in inductance and capacitance

D. changes in stored energy in inductance and capacitance

The phase angle of a series RL circuit may be computed as ___ or ___ or ___. A. cos^-1 R/XL, sin^-1 XL/R, tan^-1 R/Z B. cos^-1 R/Z, sin^-1 XL/R, tan^-1 R/XL C. cos^-1 Z/XL, sin^-1 R/Z, tan^-1 XL/R D. cos^-1 R/Z, sin^-1 XL/Z, tan^-1 XL/R

D. cos^-1 R/Z, sin^-1 XL/Z, tan^-1 XL/R

For an RL circuit, the power factor cannot be less than ___ or greater than ___. A. 0, 1 B. 1, 0 C. 0, -1 D. -1, 0

A. 0, 1

To a series RLC circuit, a voltage of 10 V is applied. If Q of the coil at resonant frequency is 20, the voltage across the inductor at resonant frequency will be A. 200 V B. 100 V C. 75 V D. 50 V

A. 200 V

The exact natural frequency of free oscillations in an oscillatory circuit with capacitance of 0.055 uF, inductance 2uH and resistance 1 ohm will be A. 478 kHz B. 337 kHz C. 272 kHz D. 192 kHz

A. 478 kHz

In the impedance triangle, the inductive reactance and impedance phasor are analogous to the ___ and ___ phasor respectively in the voltage triangle. A. inductive voltage, total voltage B. inductive current, total current C. inductive voltage, resistive voltage D. inductive current, resistive current

A. inductive voltage, total voltage

The current in RLC series circuit, i.e. at resonance is A. maximum B. minimum C. infinity D. zero

A. maximum

In RLC circuits, the current at resonance is A. maximum in series circuit and minimum in parallel circuit B. maximum in parallel circuit and minimum in series circuit C. maximum in both circuits D. minimum in both circuits

A. maximum in series circuit and minimum in parallel circuit

In series as well as parallel resonant circuits, increasing the value of resistance would lead to A. increase in the bandwidth of both the circuits B. decrease in the bandwidth of both the circuits C. increase in bandwidth in series circuit and decrease in parallel circuit D. decrease in bandwidth in series circuit and increase in parallel circuit

D. decrease in bandwidth in series circuit and increase in parallel circuit

A coil with large distributed capacitance has a A. low resistance B. low Q C. low resonant frequency D. high resonant frequency

D. high resonant frequency

For a series RLC circuit at resonance the current amplitude is ___ for a fixed voltage amplitude and the power factor is ___. A. minimum, zero B. minimum, unity C. maximum, zero D. maximum, unity

D. maximum, unity

The impedance triangle is similar to the ___ triangle with the resistance phasor in place of the ___. A. current, resistor current B. current, resistor voltage C. voltage, impedance D. voltage, resistor voltage

D. voltage, resistor voltage

The impedance of a series RLC circuit is A. √R^2 + XL^2 + XC^2 B. √R^2 + XL^2 - XC^2 C. √R^2 + (XL + XC)^2 D. √R^2 + (XL - XC)^2

D. √R^2 + (XL - XC)^2