E5D: AC and RF energy in real circuits: skin effect; electrostatic and electromagnetic fields; reactive power; power factor; coordinate systems
E5D01:
What is the result of skin effect?
As frequency increases, RF current flows in a thinner layer of the conductor, closer to the surface
As frequency decreases, RF current flows in a thinner layer of the conductor, closer to the surface
Thermal effects on the surface of the conductor increase the impedance
Thermal effects on the surface of the conductor decrease the impedance
E5D02:
Why is the resistance of a conductor different for RF currents than for direct currents?
Because of skin effect
Because the insulation conducts current at high frequencies
Because of the Heisenburg Effect
Because conductors are non-linear devices
E5D03:
What device is used to store electrical energy in an electrostatic field?
A capacitor
A battery
A transformer
An inductor
E5D04:
What unit measures electrical energy stored in an electrostatic field?
Joule
Coulomb
Watt
Volt
E5D05:
What is a magnetic field?
The region surrounding a magnet through which a magnetic force acts
Electric current through the space around a permanent magnet
The space between the plates of a charged capacitor, through which a magnetic force acts
The force that drives current through a resistor
E5D06:
In what direction is the magnetic field oriented about a conductor in relation to the direction of electron flow?
In a direction determined by the left-hand rule
In the same direction as the current
In a direction opposite to the current
In all directions; omnidirectional
E5D07:
What determines the strength of a magnetic field around a conductor?
The amount of current
The resistance divided by the current
The ratio of the current to the resistance
The diameter of the conductor
E5D08:
What is the term for energy that is stored in an electromagnetic or electrostatic field?
Potential energy
Amperes-joules
Joules-coulombs
Kinetic energy
E5D09:
What is the term for an out-of-phase, nonproductive power associated with inductors and capacitors?
Reactive power
Effective power
True power
Peak envelope power
E5D10:
In a circuit that has both inductors and capacitors, what happens to reactive power?
It is repeatedly exchanged between the associated magnetic and electric fields, but is not dissipated
It is dissipated as heat in the circuit
It is dissipated as kinetic energy in the circuit
It is dissipated in the formation of inductive and capacitive fields
E5D11:
How can the true power be determined in an AC circuit where the voltage and current are out of phase?
By multiplying the apparent power times the power factor
By dividing the reactive power by the power factor
By dividing the apparent power by the power factor
By multiplying the reactive power times the power factor
E5D12:
What is the power factor of an R-L circuit having a 60 degree phase angle between the voltage and the current?
0.5
1.414
0.866
1.73
E5D13:
How many watts are consumed in a circuit having a power factor of 0.2 if the input is 100-V AC at 4 amperes?
80 watts
400 watts
2000 watts
50 watts
E5D14:
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?
100 Watts
70.7 Watts
141.4 Watts
200 Watts
E5D15:
What is reactive power?
Wattless, nonproductive power
Power consumed in wire resistance in an inductor
Power lost because of capacitor leakage
Power consumed in circuit Q
E5D16:
What is the power factor of an RL circuit having a 45 degree phase angle between the voltage and the current?
0.707
0.866
1.0
0.5
E5D17:
What is the power factor of an RL circuit having a 30 degree phase angle between the voltage and the current?
0.866
1.73
0.5
0.577
E5D18:
How many watts are consumed in a circuit having a power factor of 0.6 if the input is 200V AC at 5 amperes?
600 watts
200 watts
1000 watts
1600 watts
E5D19:
How many watts are consumed in a circuit having a power factor of 0.71 if the apparent power is 500 watts?
355 W
704 W
252 W
1.42 mW
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