ELECTRICAL CIRCUITS Multiple Choice Questions Part 3.

1 What is the temperature coefficient of the resistance Eureka?
Infinity
Negative
Almost zero
Positive

2 If resonant frequency is 10 kHz and quality factor is 50, then
Bandwidth is 200 Hz
XL = is 50,000 fi
R is 50 fi
XC = is 50,000 fi

3 The voltage lags the current by n cycle in a

Purely resistive circuit
Purely inductive circuit
Purely capacitive circuit
Circuit containing resistance, capacitance and inductance

4 What is the half-power bandwidth of a parallel resonant circuit which has a resonant frequency of 3.6 MHz and Q of 218?
1.65 kHz
16.5 MHz
16.5 kHz
165 kHz

5 Which one of the following elements serves as a protection against overload?
Fuse
Switch
Resistor
Relay

6 What capacitance exists not through design but simply because two conducting surfaces
are relatively close to each other?
Surge
Stray
Natural
Normal

7 If three 100-pF capacitors are connected in series, then the total capacitance is
300 pF
100 pF
50 pF
33.3 pF

8 An inductance of 1 mH is
⦁      0.001 H
⦁      0.01 H
⦁      0.0001 H
⦁      0.10 H

9 The unit of elastance is
Daraf
Siemen
Henry

10 The farad is not equivalent to which of the following combination of units
CV2
C2/J
C/V
J/V2

11 In an RL series circuit,
Current lags voltage by less than 90˚
Current lags voltage by 180˚
Current lags voltage by 90˚

12 In a pure capacitance,
Current lags voltage by 90˚
Current lags voltage by 180˚

13 Which of the following elements is active?
Resistor
Inductor
Capacitor
Ideal voltage source

14 What is the complex impedance of a circuit with an absolute resistance of 300 fi?
0 + j 300 fi
⦁      300 + j 90 fi
0 – j 300 fi
300 + j 0 fi

15 The Q-factor of a parallel resonant circuit is also known as
Current magnification factor
Voltage magnification factor
Leakage factor

16 The Q-factor of a series resonant circuit is also known as
Current magnification factor
Voltage magnification factor
Leakage factor

17 An electric circuit contains
Passive elements
Active elements
Both active and passive elements
Reactive elements

18 What is the hot resistance of a 100 W, 220 V incandescent lamp?
2.2 fi
22 fi
484 fi
4.84 fi

19 What is a closed path made of several branches of the network called?
Junction
Node
Terminal
Loop

20 The internal resistance of an ideal voltage source is
Infinite
Zero
To be determined

21 What value of R is needed with a 0.05 µF C for an RC time constant of 0.02 s?
400 fi
400 Mfi
400 Gfi
400 kfi

22 Which of the following is the statement of Ohm’s law?
Electric current is directly proportional to both voltage and resistance
Electric current varies directly as the voltage and inversely as the resistance
Electrical power is directly proportional to the resistance and inversely as the current squared
Electrical power is directly proportional to both voltage squared and the resistance

23 A real current source has
Infinite internal resistance
Zero internal resistance
Large internal resistance
Small internal resistance

24 What is the cross-sectional are of a conductor whose diameter is 0.001 inch?
One micron
One angstrom
One circular mil

25 Which of the following describes the action of a capacitor?
Stores electrical energy
Opposes changes in current flow
Creates a dc resistance
Converts ac to dc

26 A rheostat is a form of
Variable resistor
Variable capacitor
Potentiometer
Thermocouple

27 Metal tin becomes superconductor at approximately
6 K
3.7 K
5 K
4.7 K

28 The Q-factor of a parallel resonant circuit is also known as
Voltage magnification factor
Current magnification factor
Gain magnification factor
Resonance magnification factor

29 What is the specific resistance of a pure silicon?
55 fi-mm
55 fi-m
55 fi-cm
55 kfi-m

30 Capacitance increase with
Larger plate area and less distance between plates
Larger plate area and greater distance between plates
Smaller plate area and less distance between plates
Higher values of applied voltage

31 What is the resonant frequency of a circuit when L of 3 microhenrys and C of 40 picofarads are in series?
14.5 kHz
145 MHz
14.5 MHz
145 kHz

32 For a triangular and sawtooth waveform the rms voltage or current equals
0.707 times peak value
0.577 times peak value
0.577 times average value
0.707 times rms value

33 If two resistances of 9 fi and 6 fi are connected in parallel, the total resistance is
54 fi
0.3 fi
15 fi
3.6 fi

34 Which of the following is a preferred resistor value?
⦁      520
⦁      47
⦁      43,000
⦁      54,321

35 A three-by-three, series-parallel matrix of resistors, all having the same ohmic value, would have a net resistance of
One-third the value of a single resistor
Three times the value of a single resistor
The same value as a single resistor
Nine times the value of a single resistor

36 The electric field strength between capacitor plates has a unit of
Volts per meter
Volts per mil
Amperes per meter
Amperes per mil

37 For multi-plate capacitor, capacitance is proportional to
Number of plates less one(n – 1)
Number of plates plus one(n + 1)
Number of plates less two(n - 2)
Number of plates (n)

38 A capacitor consists of two
Conductors only
Dielectric only
Conductors separated by a dielectric
Dielectric separated by a conductor

39 In an ac circuit with inductive reactance, the
Phase angle of the circuit is always 45˚
Voltage across the inductance must be 90˚ out-of-phase with the applied voltage
Current through the inductance lags its induced voltage by 90˚
Current through the inductance and voltage across it are180˚ out-of-phase

40 If three 9 mH inductors are connected in parallel without mutual inductance then the total inductance is
3 mH
9 mH
27 mH
18 mH

41 A series RLC circuit has a power factor at its half-power points
Unity
Lagging
Either B or C

42 Kirchhoff’s laws (KCL and KVL) are applicable to
DC circuits
AC circuits
DC as well as AC circuits
Passive networks alone

43 In calculating maximum instantaneous power voltage or current is used.
Peak
Average
Rms
Instantaneous

44 The area of capacitor plates increases two times, then its capacitance
Increases two times
Increases four times
Decreases two times
Decreases four times

45 In Norton’s theorem, the short circuit current is obtained by
Opening the voltage source
Shorting the voltage source

46 For maximum power transfer, what is the relation between load resistance RL and internal resistance R of the voltage source?
RL = 2 r
RL = 1.5 r
RL = r
RL = 3 r

47 What is a rotating vector whose projection can represent either current or voltage
in an ac circuit?
Polar diagram
Scalar quantity
Velocity
Phasor

48 Which factor does not affect resistance?
Length
Resistivity
Cross-sectional area
Mass

49 Which of the following capacitors are used only in dc circuits?
Mica
Ceramic
Mylar
Electrolytic

50 The maximum power transfer theorem is used in
Power system
Electronic system
Refrigeration
Air conditioning