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

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effective 7/01/2016 thru 6/29/2020

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2016-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

2016-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

2016-E5D02:
Why is it important to keep lead lengths short for components used in circuits for VHF and above?

To avoid unwanted inductive reactance

To increase the thermal time constant

To maintain component lifetime

All of these choices are correct

2016-E5D03:
What is microstrip?

Precision printed circuit conductors above a ground plane that provide constant impedance interconnects at microwave frequencies

Lightweight transmission line made of common zip cord

Miniature coax used for low power applications

Short lengths of coax mounted on printed circuit boards to minimize time delay between microwave circuits

2016-E5D04:
Why are short connections necessary at microwave frequencies?

To reduce phase shift along the connection

To increase neutralizing resistance

Because of ground reflections

To reduce noise figure

2016-E5D05:
Which parasitic characteristic increases with conductor length?

Inductance

Permeability

Permittivity

Malleability

2016-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; omni-directional

2016-E5D07:
What determines the strength of the magnetic field around a conductor?

The amount of current flowing through the conductor

The resistance divided by the current

The ratio of the current to the resistance

The diameter of the conductor

2016-E5D08:
What type of energy is stored in an electromagnetic or electrostatic field?

Potential energy

Electromechanical energy

Thermodynamic energy

Kinetic energy

2016-E5D09:
What happens to reactive power in an AC circuit that has both ideal inductors and ideal capacitors?

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

2016-E5D10:
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

2016-E5D11:
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

2016-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?

80 watts

400 watts

2000 watts

50 watts

2016-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?

100 Watts

70.7 Watts

141.4 Watts

200 Watts

2016-E5D14:
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

2016-E5D15:
What is the power factor of an R-L circuit having a 45 degree phase angle between the voltage and the current?

0.707

0.866

1.0

0.5

2016-E5D16:
What is the power factor of an R-L circuit having a 30 degree phase angle between the voltage and the current?

0.866

1.73

0.5

0.577

2016-E5D17:
How many watts are consumed in a circuit having a power factor of 0.6 if the input is 200VAC at 5 amperes?

600 watts

200 watts

1000 watts

1600 watts

2016-E5D18:
How many watts are consumed in a circuit having a power factor of 0.71 if the apparent power is 500VA?