Instructor Joe Seibert, AL1F

Volts and Amps

Names of electrical units: DC and AC

Electrical current is measured in the following units: Amperes

The name for the flow of electrons in an electric circuit is: Current

The name for a current that flows only in one direction is: Direct Current (DC)

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Metric PrefixesMetric Exponent EnglishTera 1012 TrillionGiga 109 BillionMega 106 Million

Kilo 103 ThousandCenti 10-2 HundredthMilli 10-3 ThousandthMicro 10-6 MillionthNano 10-9 BillionthPico 10-12 Trillionth

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Volts and Amps

Units, kilo, mega, milli, micro

One thousand volts is equal to one kilovolt.

Another way to specify the frequency of a radio signal that is oscillating at 1,500,000 Hertz is 1500 kHz [or 1.5 megahertz]

1500 milliamperes is the same as 1.5 amperes.

A hand-held transceiver that has an output power of 500 milliwatts can otherwise be said to output 0.5 watts.

One one-millionth of a volt is equal to one microvolt.

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Volts and Amps

Names of electrical units: DC and AC

Electrical Power is measured in the following units: Watt

The standard unit of frequency is: Hertz

The basic unit of resistance is: Ohm

The name for current that reverses direction on a regular basis is: Alternating Current (AC)

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Multimeters will measure Voltage, Current and Resistance.

Be sure it is set properly to read what is being measured.

If it is set to the ohms setting and voltage is measured the meter could be damaged!

Volts and Amps Conductors and insulators

Copper is a good electrical conductor.

Glass is a good electrical insulator.

The term used to describe opposition to current flow in ordinary conductors such as wires is: Resistance.

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Volts and Amps Two types of electricity:

Direct Current - flows in 1 direction Battery

1.5 to 2.5 volts per cell Car battery nominal 12 volts

Measured strictly by amplitudeAlternating Current - alternates direction

Household Measured by

Average Amplitude Frequency (cycles per second)(Hertz)

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Alternating & Direct Current

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time

V+

V-

0V

AC

DC

Volts and Amps

Electrical componentsAn automobile battery usually supplies about

12 volts [DC].An Ammeter is an instrument used to measure

the flow of current in an electrical circuit.A Voltmeter is an instrument used to measure

Electromotive Force (EMF) between two points such as the poles of a battery.

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Volts and Amps

Ammeters must beconnected in lineTo measure current

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Power Supply

Transceiver

Ammeter

Volts and Amps

Volt meters must be connectedacross a load to Measure the voltage

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Ohmmeter

Volts and AmpsOhms law relationships

The formula, Voltage (E) equals current (I) multiplied by resistance (R).

E = I*R

The formula, Current (I) equals voltage (E) divided by resistance (R). I = E/R

The formula, Resistance (R) equals voltage (E) divided by current (I). R = E/I

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Meter Excercise

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+

Meter A

Meter BR

What circuit quantity would meter A indicate?

Battery voltage

What circuit quantity would meter B indicate?

The current flowing through the resistor

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Resistanceto current flow,

OHMS

The flow ofElectrons,AMPERES

Electromotive Force, VOLTS

EI R

Volts and Amps

Ohms law relationships

If I=3 amperes and E=90 volts. R = E/I = R = 90/3= 30

If E=12 volts and I=1.5 amperes. R = E/I = R = 12/1.5= 8

If E=120 volts and R=80 ohms. I = E/R = I = 120/80= 1.5

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Volts and Amps

Ohms law relationships

If a current of 0.5 amperes flows through a 2 ohm resistor. E=I*R E = 0.5 * 2 = 1 volt

If a current of 1 ampere flows through a 10 ohm resistor. E=I*R E = 1 * 10 = 10 volts

If a current of 2 amperes flows through a 10 ohm resistor. E=I*R E = 2 * 10 = 20 volts

Current through a 100 ohm resistor across 200 volts. I=E/R I = 200/100 = 2 amperes

Current through a 24 ohm resistor across 240 volts. I=E/R I = 240/24 = 10 amperes

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Volts and Amps

Ohms law relationships

If a current of 0.5 amperes flows through a 2 ohm resistor. E=I*R E = 0.5 * 2 = 1 volt

If a current of 1 ampere flows through a 10 ohm resistor. E=I*R E = 1 * 10 = 10 volts

If a current of 2 amperes flows through a 10 ohm resistor. E=I*R E = 2 * 10 = 20 volts

Current through a 100 ohm resistor across 200 volts. I=E/R I = 200/100 = 2 amperes

Current through a 24 ohm resistor across 240 volts. I=E/R I = 240/24 = 10 amperes

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Power

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+

Meter A

Meter BR

P = E x I

Power is measured in Watts

Ohms law states E= I x R

Substituting I x R for E in the power equation gives:

P = I x R x I = R x 2 x I = R x I2

So, for this circuit, the power consumed in the resistor can be calculated by multiplying the value of the resistor times the square of the reading of Meter B.

Volts and Amps

Power calculations

The unit used to describe electrical power

is the Watt.

The formula: Power (P) equals voltage (E)

multiplied by current (I). P = I * E 20

Volts and AmpsPower calculations

The unit used to describe electrical

power is the Watt.

The formula: Power (P) equals voltage

(E) multiplied by current (I). P = I * E 21

Volts and Amps

Power calculations You can you determine how many watts are

being drawn [consumed] by your transceiver when you are transmitting by measuring the DC voltage at the transceiver and multiplying by the current drawn when you transmit.

How many amperes is flowing in a circuit when the applied voltage is 120 volts DC and the load is 1200 watts. I = P/E I = 1200/120 = 10 amperes.

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Reminder….Unit of current… amperesElectron flow is called currentCurrent flowing in one direction is DCUnit of power … WattUnit of frequency … HertzUnit of resistance … OhmCurrent that reverses direction is AC

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Reminder ….Copper is a good conductor

Glass is a good insulator

Opposition to current flow …. Resistance

Conductors…gold, silver, copper, aluminum

Insulators…air, rubber, plastic, ceramic

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Reminder….Car battery … 12 volts DC

DC measured by amplitude

AC measured by Average Amplitude

Ammeter measures current

Volt meter measures voltage

Sixty hertz means 60 cycles per second

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Reminder… Ohms Law

Power calculations

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Reminder…One kilovolt is one thousand volts

1500 KHz is 1,500,000 Hertz

1.5 amps is 1500 milliamperes

500 milliwatts is 0.5 watts

One microvolt is one one-millionth of a volt

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Volts and Amps

Test Questions

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Electrical current is measured in which of the following units?

A. VoltsB. WattsC. OhmsD. Amperes

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Electrical Power is measured in which of the following units?

A. VoltsB. WattsC. OhmsD. Amperes

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What is the name for the flow of electrons in an electric circuit?

A. Voltage B. Resistance C. Capacitance D. Current

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What is the name of a current that flows only in one direction?

A. An alternating current B. A direct current C. A normal current D. A smooth current

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What is the standard unit of frequency?

A. The megacycleB. The HertzC. One thousand cycles per secondD. The electromagnetic force

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How much voltage does an automobile battery usually supply?

A. About 12 volts B. About 30 volts C. About 120 volts D. About 240 volts

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What is the basic unit of resistance?

A. The volt B. The watt C. The ampere D. The ohm

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What is the name of a current that reverses direction on a regular basis?

A. An alternating current B. A direct current C. A circular current D. A vertical current

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Which of the following is a good electrical conductor?

A. GlassB. WoodC. CopperD. Rubber

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Which of the following is a good electrical insulator?

A. CopperB. GlassC. AluminumD. Mercury

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What is the frequency range of the 6 meter band in the United States?

A. 144 to 148 MHzB. 222 to 225 MHzC. 420 to 450 MHzD. 50 to 54 MHz

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T4A11 What is the term used to describe opposition to current flow in

ordinary conductors such as wires?

A. InductanceB. ResistanceC. Counter EMFD. Magnetism

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T4A12 What instrument is used to measure the flow of current in an

electrical circuit?

A. Frequency meterB. SWR meterC. AmmeterD. Voltmeter

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What instrument is used to measure Electromotive Force (EMF) between two points such as the poles of a battery?

A. MagnetometerB. VoltmeterC. AmmeterD. Ohmmeter

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What is the name for the distance a radio wave travels during one complete cycle?

A. Wave speedB. WaveformC. WavelengthD. Wave spread

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What term describes the number of times that an alternating current flows back and forth per second?

A. Pulse rate B. Speed C. Wavelength D. Frequency

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What does 60 hertz (Hz) mean?A. 6000 cycles per secondB. 60 cycles per secondC. 6000 meters per secondD. 60 meters per second

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Electromagnetic waves that oscillate more than 20,000 times per second as they travel through space are generally referred to as what?

A. Gravity wavesB. Sound wavesC. Radio wavesD. Gamma radiation

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How fast does a radio wave travel through space?

A. At the speed of lightB. At the speed of soundC. Its speed is inversely proportional to its

wavelengthD. Its speed increases as the frequency

increases

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How does the wavelength of a radio wave relate to its frequency?

A. The wavelength gets longer as the frequency increases

B. The wavelength gets shorter as the frequency increases

C. There is no relationship between wavelength and frequency

D. The wavelength depends on the bandwidth of the signal

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What is the formula for converting frequency to wavelength in meters?

A. Wavelength in meters equals frequency in Hertz multiplied by 300

B. Wavelength in meters equals frequency in Hertz divided by 300

C. Wavelength in meters equals frequency in megahertz divided by 300

D. Wavelength in meters equals 300 divided by frequency in megahertz

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What are sound waves in the range between 300 and 3000 Hertz called?

A. Test signalsB. Ultrasonic wavesC. Voice frequenciesD. Radio frequencies

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What property of a radio wave is often used to identify the different bands amateur radio operators use?

A. The physical length of the waveB. The magnetic intensity of the waveC. The time it takes for the wave to travel one

mileD. The voltage standing wave ratio of the wave

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What is the frequency range of the 2 meter band in the United States?

A. 144 to 148 MHzB. 222 to 225 MHzC. 420 to 450 MHzD. 50 to 54 MHz

Electrical current is measured in which of the following units?

A. VoltsB. WattsC. OhmsD. Amperes

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What is the frequency range of the 70 centimeter band in the United States?

A. 144 to 148 MHzB. 222 to 225 MHzC. 420 to 450 MHzD. 50 to 54 MHz

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What is used to convert radio signals into sounds we can hear?

A. TransmitterB. ReceiverC. MicrophoneD. Antenna

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What is used to convert sounds from our voice into radio signals?

A. TransmitterB. ReceiverC. SpeakerD. Antenna

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What two devices are combined into one unit in a transceiver?

A. Receiver, transmitterB. Receiver, transformerC. Receiver, transistorD. Transmitter, deceiver

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What device is used to convert the alternating current from a wall outlet into low-voltage direct current?

A. InverterB. CompressorC. Power SupplyD. Demodulator

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What device is used to increase the output of a 10 watt radio to 100 watts?

A. AmplifierB. Power supplyC. AntennaD. Attenuator

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Which of the battery types listed below offers the longest life when used with a hand-held radio, assuming each battery is the same physical size?

A. Lead-acid B. AlkalineC. Nickel-cadmiumD. Lithium-ion

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What is the nominal voltage per cell of a fully charged nickel-cadmium battery?

A. 1.0 voltsB. 1.2 voltsC. 1.5 voltsD. 2.2 volts

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What battery type on this list is not designed to be re-charged?

A. Nickel-cadmiumB. Carbon-zincC. Lead-acid D. Lithium-ion

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What is required to keep rechargeable batteries in good condition and ready for emergencies?

A. They must be inspected for physical damage and replaced if necessary

B. They should be stored in a cool and dry location

C. They must be given a maintenance recharge at least every 6 months

D. All of these answers are correct

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What is the best way to get the most amount of energy from a battery?

A. Draw current from the battery as rapidly as possible

B. Draw current from the battery at the slowest rate needed

C. Reverse the leads when the battery reaches the 1/2 charge level

D. Charge the battery as frequently as possible

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What formula is used to calculate current in a circuit?

A. Current (I) equals voltage (E) multiplied by resistance (R)

B. Current (I) equals voltage (E) divided by resistance (R)

C. Current (I) equals voltage (E) added to resistance (R)

D. Current (I) equals voltage (E) minus resistance (R)

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What formula is used to calculate voltage in a circuit?

A. Voltage (E) equals current (I) multiplied by resistance (R)

B. Voltage (E) equals current (I) divided by resistance (R)

C. Voltage (E) equals current (I) added to resistance (R)

D. Voltage (E) equals current (I) minus resistance (R)

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What formula is used to calculate resistance in a circuit?

A. Resistance (R) equals voltage (E) multiplied by current (I)

B. Resistance (R) equals voltage (E) divided by current (I)

C. Resistance (R) equals voltage (E) added to current (I)

D. Resistance (R) equals voltage (E) minus current (I)

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What is the resistance of a circuit when a current of 3

amperes flows through a resistor connected to 90 volts?

A. 3 ohms B. 30 ohms C. 93 ohms D. 270 ohms

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What is the resistance in a circuit where the applied voltage is 12 volts and the current flow is 1.5 amperes?

A. 18 ohmsB. 0.125 ohms C. 8 ohmsD. 13.5 ohms

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What is the current flow in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms?

A. 9600 amperesB. 200 amperesC. 0.667 amperesD. 1.5 amperes

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What is the voltage across the resistor if a current of 0.5 amperes flows through a 2 ohm resistor?

A. 1 voltB. 0.25 voltsC. 2.5 voltsD. 1.5 volts

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What is the voltage across the resistor if a current of 1 ampere flows through a 10 ohm resistor?

A. 10 voltsB. 1 voltC. 11 voltsD. 9 volts

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What is the voltage across the resistor if a current of 2 amperes flows through a 10 ohm resistor?

A. 20 voltsB. 0.2 voltsC. 12 voltsD. 8 volts

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What is the current flowing through a 100 ohm resistor connected across 200 volts?

A. 20,000 amperesB. 0.5 amperesC. 2 amperesD. 100 amperes

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What is the current flowing through a 24 ohm resistor connected across 240 volts?

A. 24,000 amperesB. 0.1 amperesC. 10 amperesD. 216 amperes

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What unit is used to describe electrical power?

A. OhmB. FaradC. VoltD. Watt

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What is the formula used to calculate electrical power?

A. Power (P) equals voltage (E) multiplied by current (I)

B. Power (P) equals voltage (E) divided by current (I)

C. Power (P) equals voltage (E) minus current (I)D. Power (P) equals voltage (E) plus current (I)

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How much power is represented by a voltage of 13.8 volts and a current of 10 amperes?

A. 138 wattsB. 0.7 wattsC. 23.8 wattsD. 3.8 watts

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How many milliamperes is the same as 1.5 amperes?

A. 15 milliamperesB. 150 milliamperesC. 1500 milliamperesD. 15000 milliamperes

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What is another way to specify the frequency of a radio signal that is oscillating at 1,500,000 Hertz?

A. 1500 kHzB. 1500 MHzC. 15 GHz D. 150 kHz

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How many volts are equal to one kilovolt?

A. one one-thousandth of a voltB. one hundred voltsC. one thousand voltsD. one million volts

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How many volts are equal to one microvolt?

A. one one-millionth of a voltB. one million voltsC. one thousand kilovolts D. one one-thousandth of a volt

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How many watts does a hand-held transceiver put out if the output power is 500 milliwatts?

A. 0.02 wattsB. 0.5 wattsC. 5 wattsD. 50 watts