Sub Element G5: Electrical Principles Flashcards
What is impedance?
The opposition to the flow of current in an AC circuit
What is reactance?
Opposition to the flow of alternating current caused by capacitance or inductance
Which of the following causes opposition to the flow of alternating current in an inductor?
Reactance
Which of the following causes opposition to the flow of alternating current in a capacitor?
Reactance
How does an inductor react to AC?
As the frequency of the applied AC increases, the reactance increases
How does a capacitor react to AC?
As the frequency of the applied AC increases, the reactance decreases
What happens when the impedance of an electrical load is equal to the output impedance of a power source, assuming both impedances are resistive?
The source can deliver maximum power to the load
What is one reason to use an impedance matching transformer?
To maximize the transfer of power
What unit is used to measure reactance?
Ohm
Which of the following devices can be used for impedance matching at radio frequencies?
A transformer
A Pi-network
A length of transmission line
All these choices are correct
Which of the following describes one method of impedance matching between two AC circuits?
Insert an LC network between the two circuits
What dB change represents a factor of two increase or decrease in power?
Approximately 3 dB
How does the total current relate to the individual currents in each branch of a purely resistive parallel circuit?
It equals the sum of the currents through each branch
How many watts of electrical power are used if 400 VDC is supplied to an 800 ohm load?
200 watts
How many watts of electrical power are used by a 12 VDC light bulb that draws 0.2 amperes?
2.4 watts
How many watts are dissipated when a current of 7.0 milliamperes flows through a 1250 ohm resistance?
Approximately 61 milliwatts
What is the output PEP from a transmitter if an oscilloscope measures 200 volts peak-to-peak across a 50 ohm dummy load connected to the transmitter output?
100 watts