What is a rotating vector whose projection can represent either current or voltage in an ac circuit?
Polar diagram
Scalar quantity
Velocity
Phasor
Correct Answer :
D. Phasor
Related Questions
What is the specific resistance of a pure germanium?
55 -cm
55 -m
55 -mm
55 k -m
It is impossible to change the voltage across a capacitor instantlya as this would produce ___ current.
Infinite
Zero
Low
High
Which of the following is a preferred resistor value?
43a000
54a321
The symbol Q refers to
Resonance quotient
Quality factor
Power quotient
Qualification test
What is expected when two 20 k a 1 watt resistor in parallel are use instead of one 10 k a 1 watt?
Provides higher current
Provides less power
Provides more power
Provides wider tolerance
Which of the following materials has the lowest dielectric strength?
Glass
Paper
Mica
Teflon
When two pure sine waves of the same frequency and the same amplitude which are exactly 180� outof-phase are added togethera the result is
A wave with twice the amplitude
A wave with half the amplitude
Zero signal
A wave with twice the frequency
In an ac circuit with inductive reactance ?, the
Phase angle of the circuit is always 45�
Voltage across the inductance must be 90� out o f-phase witht he applied voltage
Current through the inductance lags its induced voltage by 90�
Current through the inductance and voltage across it are180� outof-phase
Which of the following is a disadvantage of a wire-wound resistor?
It has reactance in radio-frequency circuits
It cannot handle much power
It draws a large amount of current
It cannot handle high voltage
When the net reactance in a series coil-capacitor circuit is zero at frequency fa the nature of its reactance of frequency 2f is
Inductive
Capacitive
Resistive
Infinite
A series RL circuit has R of 10 and XL of 5 a its impedance in rectangular form is given by
10 +j 5
10 + j 10
10 ± j 5
10 ± j 10
When the movable plates of a gang capacitor completely overlap the fixed platesa the capacitance of the capacitor is
Halfway between maximum and minimum
Maximum
Minimum
Zero
If the capacitance of mica capacitor is 5 times the capacitcitora then the relative permittivity of mica is
The distance between the capacitor plates increases two timesa then its capacitance
Increases two times
Increases four times
Decreases two times
Decreases four times
Kirchhoff�s laws (KCL and KVL) are applicable to
DCcircuits
ACcircuits
DC as well as AC circuits
Passive networks alone
When two coils of identical reactance are in parallel without mutual inductancea the reactance of the combination is ___ the reactance of each coil.
One half
Twice
Four times
One fourth
In an ac circuit with XL and R in seriesa the
Voltages across R and XL are in phase
Voltage across R lags the voltage across XLby 90°
Voltages across R and XL are 180° outof-phase
Voltage across R leads the voltage across XLby 90°
For a carbon composition resistora typical resistance values range from
2.7 to 22 M
1000 to 10000
10 to 10 M
2.7 to 2.7G
An open resistor when checked with an ohmmeter reads
Zero
Infinite
High but within the tolerance
Low but not zero
What is the resonant frequency of a circuit when L of 25 microhenrys and C of 10 picofarads are in parallel?
10.1 kHz
10.1 MHz
101 MHz
101 kHz
What is the peak factor for alternating current or voltage varying sinusiodally?
Which of the following is not a factor affecting dielectric strength?
Mass
Moisture content
Temperature
Thickness
The power factor of a certain circuit in which the voltage lags behind the current is 80 %. To increase the power to 100 %a it is necessary to add ___ to the circuit.
Inductance
Capacitance
Resistance
Impedance
A term used to express the amount of electrical energy stored in electrostatic field.
Joules
Coulombs
Watts
Electron-volt
The Q-factor of a series resonant circuit is also known as
Current magnification factor
Voltage magnification factor
Load factor
Leakage factor
What is the time constant for L of 240 mH in series with R of 20 ?
12 ms
4.8 s
83.3 s
12 s
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
Loop currents should be assumed to flow in which direction
Straight
Clockwise
Counter-clockwise
Either B or C arbitrarily selected
Which of the following combination of length and cross-sectional area will give a certain volume of copper the least resistance?
2L and1/2 A
Does not matter because the volume of copper remains the same
L and A
½ L and 2 A
Transient period is considered over after