# Extra Class License Exam Questions

### Subelement E5

Electrical Principles

#### Groups

- E5A - Resonance and Q: characteristics of resonant circuits: series and parallel resonance; definitions and effects of Q; half-power bandwidth; phase relationships in reactive circuits
- E5B - Time constants and phase relationships: RLC time constants; definition; time constants in RL and RC circuits; phase angle between voltage and current; phase angles of series RLC; phase angle of inductance vs susceptance; admittance and susceptance
- E5C - Coordinate systems and phasors in electronics: Rectangular Coordinates; Polar Coordinates; Phasors
- E5D - AC and RF energy in real circuits: skin effect; electrostatic and electromagnetic fields; reactive power; power factor; electrical length of conductors at UHF and microwave frequencies

Question Display Options:

Group E5A
Resonance and Q: characteristics of resonant circuits: series and parallel resonance; definitions and effects of Q; half-power bandwidth; phase relationships in reactive circuits

E5A01
What can cause the voltage across reactances in series to be larger than the voltage applied to them?

E5A02
What is resonance in an electrical circuit?

E5A03
What is the magnitude of the impedance of a series RLC circuit at resonance?

E5A04
What is the magnitude of the impedance of a circuit with a resistor, an inductor and a capacitor all in parallel, at resonance?

E5A05
What is the magnitude of the current at the input of a series RLC circuit as the frequency goes through resonance?

E5A06
What is the magnitude of the circulating current within the components of a parallel LC circuit at resonance?

E5A07
What is the magnitude of the current at the input of a parallel RLC circuit at resonance?

E5A08
What is the phase relationship between the current through and the voltage across a series resonant circuit at resonance?

E5A09
How is the Q of an RLC parallel resonant circuit calculated?

E5A10
How is the Q of an RLC series resonant circuit calculated?

E5A11
What is the half-power bandwidth of a parallel resonant circuit that has a resonant frequency of 7.1 MHz and a Q of 150?

E5A12
What is the half-power bandwidth of a parallel resonant circuit that has a resonant frequency of 3.7 MHz and a Q of 118?

E5A13
What is an effect of increasing Q in a resonant circuit?

E5A14
What is the resonant frequency of a series RLC circuit if R is 22 ohms, L is 50 microhenrys and C is 40 picofarads?

E5A15
Which of the following can increase Q for inductors and capacitors?

E5A16
What is the resonant frequency of a parallel RLC circuit if R is 33 ohms, L is 50 microhenrys and C is 10 picofarads?

E5A17
What is the result of increasing the Q of an impedance-matching circuit?

Group E5B
Time constants and phase relationships: RLC time constants; definition; time constants in RL and RC circuits; phase angle between voltage and current; phase angles of series RLC; phase angle of inductance vs susceptance; admittance and susceptance

E5B01
What is the term for the time required for the capacitor in an RC circuit to be charged to 63.2% of the applied voltage?

E5B02
What is the term for the time it takes for a charged capacitor in an RC circuit to discharge to 36.8% of its initial voltage?

E5B03
What happens to the phase angle of a reactance when it is converted to a susceptance?

E5B04
What is the time constant of a circuit having two 220 microfarad capacitors and two 1 megohm resistors, all in parallel?

E5B05
What happens to the magnitude of a reactance when it is converted to a susceptance?

E5B06
What is susceptance?

E5B07
What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 500 ohms, R is 1 kilohm, and XL is 250 ohms?

E5B08
What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 100 ohms, R is 100 ohms, and XL is 75 ohms?

E5B09
What is the relationship between the current through a capacitor and the voltage across a capacitor?

E5B10
What is the relationship between the current through an inductor and the voltage across an inductor?

E5B11
What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 25 ohms, R is 100 ohms, and XL is 50 ohms?

E5B12
What is admittance?

E5B13
What letter is commonly used to represent susceptance?

Group E5C
Coordinate systems and phasors in electronics: Rectangular Coordinates; Polar Coordinates; Phasors

E5C01
Which of the following represents a capacitive reactance in rectangular notation?

E5C02
How are impedances described in polar coordinates?

E5C03
Which of the following represents an inductive reactance in polar coordinates?

E5C04
Which of the following represents a capacitive reactance in polar coordinates?

E5C05
What is the name of the diagram used to show the phase relationship between impedances at a given frequency?

E5C06
What does the impedance 50–j25 represent?

E5C07
What is a vector?

E5C08
What coordinate system is often used to display the phase angle of a circuit containing resistance, inductive and/or capacitive reactance?

E5C09
When using rectangular coordinates to graph the impedance of a circuit, what does the horizontal axis represent?

E5C10
When using rectangular coordinates to graph the impedance of a circuit, what does the vertical axis represent?

E5C11
What do the two numbers that are used to define a point on a graph using rectangular coordinates represent?

E5C12
If you plot the impedance of a circuit using the rectangular coordinate system and find the impedance point falls on the right side of the graph on the horizontal axis, what do you know about the circuit?

E5C13
What coordinate system is often used to display the resistive, inductive, and/or capacitive reactance components of impedance?

E5C14
Which point on Figure E5-2 best represents the impedance of a series circuit consisting of a 400 ohm resistor and a 38 picofarad capacitor at 14 MHz?

E5C15
Which point in Figure E5-2 best represents the impedance of a series circuit consisting of a 300 ohm resistor and an 18 microhenry inductor at 3.505 MHz?

E5C16
Which point on Figure E5-2 best represents the impedance of a series circuit consisting of a 300 ohm resistor and a 19 picofarad capacitor at 21.200 MHz?

E5C17
Which point on Figure E5-2 best represents the impedance of a series circuit consisting of a 300 ohm resistor, a 0.64-microhenry inductor and an 85-picofarad capacitor at 24.900 MHz?

Group E5D
AC and RF energy in real circuits: skin effect; electrostatic and electromagnetic fields; reactive power; power factor; electrical length of conductors at UHF and microwave frequencies

E5D01
What is the result of skin effect?

E5D02
Why is it important to keep lead lengths short for components used in circuits for VHF and above?

E5D03
What is microstrip?

E5D04
Why are short connections necessary at microwave frequencies?

E5D05
Which parasitic characteristic increases with conductor length?

E5D06
In what direction is the magnetic field oriented about a conductor in relation to the direction of electron flow?

E5D07
What determines the strength of the magnetic field around a conductor?

E5D08
What type of energy is stored in an electromagnetic or electrostatic field?

E5D09
What happens to reactive power in an AC circuit that has both ideal inductors and ideal capacitors?

E5D10
How can the true power be determined in an AC circuit where the voltage and current are out of phase?

E5D11
What is the power factor of an R-L circuit having a 60 degree phase angle between the voltage and the current?

E5D12
How many watts are consumed in a circuit having a power factor of 0.2 if the input is 100-VAC at 4 amperes?

E5D13
How much power is consumed in a circuit consisting of a 100 ohm resistor in series with a 100 ohm inductive reactance drawing 1 ampere?

E5D14
What is reactive power?

E5D15
What is the power factor of an R-L circuit having a 45 degree phase angle between the voltage and the current?

E5D16
What is the power factor of an R-L circuit having a 30 degree phase angle between the voltage and the current?

E5D17
How many watts are consumed in a circuit having a power factor of 0.6 if the input is 200VAC at 5 amperes?

E5D18
How many watts are consumed in a circuit having a power factor of 0.71 if the apparent power is 500VA?