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Subelement T5
Electrical principles: math for electronics; electronic principles; Ohm's Law
Section T5A
Electrical principles, units, and terms: current and voltage; conductors and insulators; alternating and direct current; series and parallel circuits
Electrical current is measured in which of the following units?
  • Volts
  • Watts
  • Ohms
  • Amperes

Volts (Voltage) - Electromotive force, or potential.

Ohms - resistance

Watts - power

Amperes - Current

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Tags: electronics electrical current definitions arrl chapter 3 arrl module 4

Electrical power is measured in which of the following units?
  • Volts
  • Watts
  • Ohms
  • Amperes

Volts - Electromotive force.

Ohms - resistance.

Watts - power.

Amperes - Current.

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Tags: electronics electrical power definitions arrl chapter 3 arrl module 5

What is the name for the flow of electrons in an electric circuit?
  • Voltage
  • Resistance
  • Capacitance
  • Current

Think of this in terms of water; what do you call the flow of water? Current.

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Tags: definitions electrical current electronics arrl chapter 3 arrl module 4

What is the name for a current that flows only in one direction?
  • Alternating current
  • Direct current
  • Normal current
  • Smooth current ~

Current that flows only in one direction is found primarily in circuits that use batteries as a power source; Cars, handheld devices, etc. There is a positive and a negative. This is referred to as Direct Current, or DC.

Compare that with the electricity and current in your house, which alternates directions -- Alternating Current. There is a "Hot" and a "Neutral", but Neutral is essentially just the ground that the electricity can flow to; the current alternates in a sine wave from negative to positive.

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Tags: dc power electrical current electronics definitions arrl chapter 3 arrl module 4

What is the electrical term for the electromotive force (EMF) that causes electron flow?
  • Voltage
  • Ampere-hours
  • Capacitance
  • Inductance

Hard to add to what is already in this question, except possibly to explain what the incorrect questions actually mean. Voltage, of course, is the electrical term for the Electromotive force that causes electron flow.

Capacitance refers to the ability to store energy in a capacitor, which will then oppose a change in voltage. Inductance refers to the ability to store energy in a coil of wire, which will then oppose a change in current. Ampere- hours is a term used to indicate the capacity of a battery -- a 50 ampere-hour battery should be able to provide 1 amp for 50 hours, or 50 amps for 1 hour.

Obviously, none of these other answers could refer to Electromotive Force.

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Tags: definitions electromotive force (voltage) electronics arrl chapter 3 arrl module 4

How much voltage does a mobile transceiver typically require?
  • About 12 volts
  • About 30 volts
  • About 120 volts
  • About 240 volts

Car batteries are about \(12\) volts (technically they are closer to \(13.8\) volts), and since mobile transceivers are most commonly used in a car they are designed to run at about that. This is really convenient, because that means that if you get batteries for running your radio you can charge them by running your car.

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Tags: radio operation dc power arrl chapter 5 arrl module 12

Which of the following is a good electrical conductor?
  • Glass
  • Wood
  • Copper
  • Rubber

As a general rule of thumb, metal tends to be a good conductor. Water can be (though technically it's the minerals in the water that makes it a good conductor -- salt water is a really good conductor, whereas distilled water is a fair insulator). Most other things, and definitely glass, wood, and rubber, are insulators -- meaning that they don't conduct electricity.

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Tags: electronics electrical components arrl chapter 3 arrl module 4

Which of the following is a good electrical insulator?
  • Copper
  • Glass
  • Aluminum
  • Mercury

Most metals are good conductors; all of them conduct electricity to some extent. A conductor is something that electricity can flow through. An insulator is the opposite -- something that electricity either doesn't flow through or doesn't flow through very well.

On a ham radio test they aren't going to try to trick you by caring how good of a conductor it is, so if it's looking for a conductor look for something metallic; if it's looking for a insulator, look for something that isn't metallic. In this case, glass is the only item listed that isn't a metal, so it's the insulator.

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Tags: electronics electrical components arrl chapter 3 arrl module 4

What is the name for a current that reverses direction on a regular basis?
  • Alternating current
  • Direct current
  • Circular current
  • Vertical current

There are two types of current that you need to worry about. The kind in your house is called Alternating Current, because the current alternates (reverses) direction over time (60 times per second in the US, or 60 Hz; that's 60 times that it goes from positive to negative and back). The RMS (Root Mean Square) voltage of AC in the US is 110 volts, and we use that because it can be sent over longer distances with less loss than the other type, Direct Current.

The most common use of Direct Current, which always goes the same direction, is circuits powered by a battery, such as a car. Battery systems vary in voltage, but most often in Ham Radio (and in cars) they are 12 volts.

The other two options listed here are just to throw you off.

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Tags: ac power electrical current electronics arrl chapter 3 arrl module 4

Which term describes the rate at which electrical energy is used?
  • Resistance
  • Current
  • Power
  • Voltage

Power, also known as "watts", is equal to Voltage times Current (\(P=E \times I\)). In other words, Power is the product of the electric current at a specified amount of electromotive force. If you use a water analogy, Current could be seen as the diameter of the hose, where voltage is the amount of force available to push it through. Power would be the actual amount of water that gets through the pipe. If you want more water to go through the pipe, you can either apply more force (voltage) or make the pipe bigger (current).

Resistance is the opposition to the current flow, so it definitely could not be considered a viable answer.

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Tags: definitions electronics electrical power arrl chapter 3 arrl module 5

What is the unit of electromotive force?
  • The volt
  • The watt
  • The ampere
  • The ohm

One way to think about electricity in general is the comparison to a water pipe.

Volts = The pressure (e.g. how much "force" does the river have). Also known as the electromotive force. How much the electron wants to move in the wire.

Amps = how much water is actually flowing through the pipe. Number of electrons moving at once.

Watts = The total amount of usable water energy the pipe contains. Volts * amps = watts

Thus, as long as you know any two of these items (Amps, Volts, of Watts), you can figure out the third.

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Tags: electromotive force (voltage) definitions electronics arrl chapter 3 arrl module 4

What describes the number of times per second that an alternating current makes a complete cycle?
  • Pulse rate
  • Speed
  • Wavelength
  • Frequency

Just remember, the "Frequency" determines how "frequently" the current reverses direction.

Another way to remember is to analyze unit of each term: Pulse rate (beat per second), Speed (meter per second), Wavelength (meter), Frequency (time per second, or Hz)

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Tags: definitions radio waves arrl chapter 3 arrl module 4

In which type of circuit is current the same through all components?
  • Series
  • Parallel
  • Resonant
  • Branch

Series is correct. In series current is the same through all components.

In the animation below, the amount of voltage is indicated by the darkness of the green, and the current is represented by the "walking ant" animation.

Series Current and Voltage

The voltage is not the same everywhere in this series but the current is!

Easy way to remember the difference between series and parallel, is parallel is like train tracks they run side by side. Series is like a movie series, one episode after another.

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In which type of circuit is voltage the same across all components?
  • Series
  • Parallel
  • Resonant
  • Branch

In the animation below, the amount of voltage is indicated by the darkness of the green, and the current is represented by the "walking ant" animation.

Voltage and Current in Parallel

Notice the green is the same across all components. There is full source voltage on one side and no voltage on the other, but voltage is the same across all components because they're in parallel.

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