Technician License Class Gordon West Technician Class Manual Pages 142-149 Volts & Amps Presented by...

Technician Technician License License ClassClass

Gordon West Gordon West Technician Class Technician Class

ManualManualPages 142-149Pages 142-149

Volts & AmpsVolts & Amps

Presented byPresented by

Heart Of Texas Heart Of Texas Amateur Radio Amateur Radio

ClubClub(HOTARC)(HOTARC)

Volts & AmpsVolts & Amps 22

Electrical Voltage & CurrentElectrical Voltage & CurrentCurrentCurrent is the flow is the flow of electrons in an of electrons in an electric circuit.electric circuit.

The unit of measure The unit of measure is amperes or is amperes or ampsamps..

We measure current We measure current with an with an ammeterammeter..

Voltage is the “force” that makes electrons Voltage is the “force” that makes electrons move—causing current.move—causing current.

We measure voltage with a We measure voltage with a voltmetervoltmeter..

V R


ResistanceResistanceResistance is what opposes current, or the flow Resistance is what opposes current, or the flow of electrons. All materials have some resistance.of electrons. All materials have some resistance.

The unit of measurement for resistance The unit of measurement for resistance is the is the ohmohm..

Materials with very low resistance, allowing Materials with very low resistance, allowing electrons to move easily, are electrons to move easily, are conductorsconductors..

Copper, for example, is a good conductor.Copper, for example, is a good conductor.

Materials with very high resistance, and do not Materials with very high resistance, and do not allow electrons to flow easily, are allow electrons to flow easily, are insulatorsinsulators..

Glass, for example, is a good insulator.Glass, for example, is a good insulator.


Water Flow is a Good Analogy to Electrical Water Flow is a Good Analogy to Electrical Voltage, Current, and ResistanceVoltage, Current, and Resistance

Battery supplies voltage,like pump supplies pressure.

Wire carries current,like pipes carry water.

Resistor slows down current,like clogs in pipe slow down flow.


T4A13 T4A13 (pg 142)(pg 142)

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

B.B. VoltmeterVoltmeterC.C. AmmeterAmmeter

D.D. OhmmeterOhmmeter


T4A06 T4A06 (pg 142)(pg 142)

How much voltage does an automobile How much voltage does an automobile battery usually supply? battery usually supply?

A.A. About 12 voltsAbout 12 voltsB.B. About 30 voltsAbout 30 volts

C.C. About 120 voltsAbout 120 volts

D.D. About 240 voltsAbout 240 volts


T4A03 T4A03 (pg 142)(pg 142)

What is the name for the What is the name for the flow of electronsflow of electrons in an electric circuit? in an electric circuit?A.A. VoltageVoltage

B.B. ResistanceResistance

C.C. CapacitanceCapacitance

D.D. CurrentCurrent


Two Basic Kinds of CurrentTwo Basic Kinds of CurrentWhen electrons flow in only one direction, When electrons flow in only one direction, it is called it is called Direct Current (DC).Direct Current (DC).

Batteries are a common source of DC.Batteries are a common source of DC.

Most electronic devices are powered by DC.Most electronic devices are powered by DC.

When electrons flow alternatively in one When electrons flow alternatively in one direction, then in the opposite direction, it direction, then in the opposite direction, it is called is called Alternating Current (AC).Alternating Current (AC).

Household current is AC.Household current is AC.


Direct Current vs Alternating CurrentDirect Current vs Alternating Current

DC delivers a constant DC delivers a constant voltage, like from a voltage, like from a battery.battery.

AC voltage regularly AC voltage regularly reverses direction, reverses direction, positive to negative, positive to negative, between a maximum-between a maximum-minimum, at a certain minimum, at a certain frequency.frequency.


T4A04T4A04What is the name of a current that flows only What is the name of a current that flows only in one direction?in one direction?A.A. An alternating currentAn alternating current

B.B. A direct currentA direct currentC.C. A normal currentA normal current

D.D. A smooth currentA smooth current


T4A01 T4A01 (pg 143)(pg 143)

Electrical current is measured in which of Electrical current is measured in which of the following units?the following units?A.A. VoltsVolts

B.B. WattsWatts

C.C. OhmsOhms

D.D. AmperesAmperes


T4A12 T4A12 (pg 143)(pg 143)

What instrument is used to measure the flow What instrument is used to measure the flow of of currentcurrent in an electrical circuit? in an electrical circuit?A.A. Frequency meterFrequency meter

B.B. SWR meterSWR meter

C.C. AmmeterAmmeterD.D. VoltmeterVoltmeter


T4A09 T4A09 (pg 143)(pg 143)

Which of the following is a good electrical Which of the following is a good electrical conductor?conductor?A.A. GlassGlass

B.B. WoodWood

C.C. CopperCopperD.D. RubberRubber


T4A08 T4A08 (pg 143)(pg 143)

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

A.A. An alternating currentAn alternating currentB.B. A direct currentA direct current

C.C. A circular currentA circular current

D.D. A vertical currentA vertical current


T4A11 T4A11 (pg 143)(pg 143)

What is the term used to describe opposition What is the term used to describe opposition to current flow in ordinary conductors such to current flow in ordinary conductors such as wires?as wires?A.A. InductanceInductance

B.B. ResistanceResistanceC.C. Counter EMFCounter EMF

D.D. MagnetismMagnetism


T4A07 T4A07 (pg 143)(pg 143)

What is the basic unit of resistance?What is the basic unit of resistance?A.A. The voltThe volt

B.B. The wattThe watt

C.C. The ampereThe ampere

D.D. The ohmThe ohm Greek letter: Omega


T4A10 T4A10 (pg 144)(pg 144)

Which of the following is a Which of the following is a good electrical insulator? good electrical insulator? A.A. CopperCopper

B.B. GlassGlassC.C. AluminumAluminum

D.D. MercuryMercury


Current, Voltage, & ResistanceCurrent, Voltage, & Resistance

Just like water flowing through a hose, Just like water flowing through a hose, changes in voltage, current, and changes in voltage, current, and resistance affect each other.resistance affect each other.

The effect is mathematically expressed in The effect is mathematically expressed in Ohm's Law:Ohm's Law:

E = I x R I = E / R R = E /

I

where E = voltage, I= current, and R = resistance


Ohm’s LawOhm’s Law

Resistanceto current:

OHMS

Current, the flow of electrons:

AMPERES

Electromotive force:VOLTS

EI R


T4D02 T4D02 (pg 144)(pg 144)

What formula is used to calculate What formula is used to calculate voltagevoltage in a circuit?in a circuit?

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

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

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

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

EE

I R

E

=

I R


T4D07 T4D07 (pg 144)(pg 144)

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

A.A. 1 volt1 voltB.B. 0.25 volts0.25 volts

C.C. 2.5 volts2.5 volts

D.D. 1.5 volts1.5 volts

EE

I R

E = I R = 0.5 A 2 = 1 V


T4D08 T4D08 (pg 145)(pg 145)

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

A.A. 10 volts10 voltsB.B. 1 volt1 volt

C.C. 11 volts11 volts

D.D. 9 volts9 volts

EE

I R

E = I R = 1 A 10 = 10 V


T4D09 T4D09 (pg 145)(pg 145)

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

A.A. 20 volts20 voltsB.B. 0.2 volts0.2 volts

C.C. 12 volts12 volts

D.D. 8 volts8 volts

EE

I R

E = I R = 2 A 10 = 20 V


T4D01 T4D01 (pg 145)(pg 145)

What formula is used to calculate What formula is used to calculate currentcurrent in in a circuit? a circuit? A.A. Current (I) equals voltage (E) Current (I) equals voltage (E)

multiplied by resistance (R)multiplied by resistance (R)

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

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

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

EE

I R

E

=

I R

—


T4D06 T4D06 (pg 146)(pg 146)

What is the What is the currentcurrent flow in a circuit with an flow in a circuit with an applied voltage of 120 volts and a applied voltage of 120 volts and a resistance of 80 ohms?resistance of 80 ohms?A.A. 9600 amperes9600 amperes

B.B. 200 amperes200 amperes

C.C. 0.667 amperes0.667 amperes

D.D. 1.5 amperes1.5 amperes

EE

I R

I = E / R = 120 V / 80 = 1.5 A


T4D10 T4D10 (pg 146)(pg 146)

What is the What is the currentcurrent flowing through a flowing through a 100 ohm resistor connected across 100 ohm resistor connected across 200 volts?200 volts?A.A. 20,000 amperes20,000 amperes

B.B. 0.5 amperes0.5 amperes

C.C. 2 amperes2 amperesD.D. 100 amperes100 amperes

EE

I R

I = E / R = 200 V / 100 = 2 A


T4D11 T4D11 (pg 146)(pg 146)

What is the What is the currentcurrent flowing through flowing through a 24 ohm resistor connected a 24 ohm resistor connected across 240 volts?across 240 volts?A.A. 24,000 amperes24,000 amperes

B.B. 0.1 amperes0.1 amperes

C.C. 10 amperes10 amperes

D.D. 216 amperes216 amperes

EE

I R

I = E / R = 240 V / 24 = 10 A


T4D03 T4D03 (pg 146)(pg 146)

What formula is used to calculate What formula is used to calculate resistanceresistance in a circuit?in a circuit?A.A. Resistance (R) equals voltage (E) Resistance (R) equals voltage (E)

multiplied by current (I)multiplied by current (I)

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

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

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

EE

I R

E

=

I R

—


T4D04 T4D04 (pg 146)(pg 146)

What is the What is the resistanceresistance of a circuit when a of a circuit when a current of 3 amperes flows through a current of 3 amperes flows through a resistor connected to 90 volts?resistor connected to 90 volts?A.A. 3 ohms3 ohms

B.B. 30 ohms30 ohmsC.C. 93 ohms93 ohms

D.D. 270 ohms270 ohms

EE

I R

R = E / I = 90 V / 3 A = 30


T4D05 T4D05 (pg 147)(pg 147)

What is the resistance in a circuit where the What is the resistance in a circuit where the applied voltage is 12 volts and the current applied voltage is 12 volts and the current flow is 1.5 amperes?flow is 1.5 amperes?A.A. 18 ohms18 ohms

B.B. 0.125 ohms0.125 ohms

C.C. 8 ohms8 ohmsD.D. 13.5 ohms13.5 ohms

EE

I R

R = E / I = 12 V / 1.5 A = 8


PowerPowerWhen moving electrons do some work, power is When moving electrons do some work, power is consumed.consumed.

The unit of measurement for power is The unit of measurement for power is WattsWatts..

Power (P) is the product of current (I) and voltage Power (P) is the product of current (I) and voltage (E).(E).

P = I x E I = P / E E = P /

I

where P = power, I = current, and E = voltage.


Watt’s LawWatt’s Law

Electromotive force:

VOLTS

Current, the flow of electrons:

AMPERES

Electric power:WATTS

PI E


T4A02 T4A02 (pg 147)(pg 147)

Electrical Power is measured in which of the Electrical Power is measured in which of the following units?following units?A.A. VoltsVolts

B.B. WattsWattsC.C. OhmsOhms

D.D. AmperesAmperesW

Watts


T4E01 T4E01 (pg 147)(pg 147)

What unit is used to describe What unit is used to describe electrical power?electrical power?A.A. OhmOhm

B.B. FaradFarad

C.C. VoltVolt

D.D. WattWattW

Watts


T4E02 T4E02 (pg 147)(pg 147)

What is the formula used to calculate What is the formula used to calculate electrical power in a DC circuit?electrical power in a DC circuit?

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

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

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

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

P

I E


T4E03 T4E03 (pg 147)(pg 147)

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

A.A. 138 watts138 wattsB.B. 0.7 watts0.7 watts

C.C. 23.8 watts23.8 watts

D.D. 3.8 watts3.8 watts

P

I E

P = I E = 10 A 13.8 V = 138 W


T4E04 T4E04 (pg 147)(pg 147)

How much How much powerpower is being used in a circuit is being used in a circuit when the voltage is 120 volts DC and the when the voltage is 120 volts DC and the current is 2.5 amperes?current is 2.5 amperes?A.A. 1440 watts1440 watts

B.B. 300 watts300 wattsC.C. 48 watts48 watts

D.D. 30 watts30 watts

P

I E

P = I E = 2.5 A 120 V = 300 W


T4E05 (pg 148)T4E05 (pg 148)How can you determine How can you determine how many wattshow many watts are are being drawn by your transceiver when you being drawn by your transceiver when you are transmitting?are transmitting?A.A. Measure the DC voltageMeasure the DC voltage

and divide it by 60 Hz and divide it by 60 HzB.B. Check the fuse in the power Check the fuse in the power

leads to see what size it isleads to see what size it isC.C. Look in the Radio Amateur's HandbookLook in the Radio Amateur's Handbook

D.D. Measure the DC Measure the DC voltagevoltage at the at the transceiver and transceiver and multiply by the multiply by the currentcurrent drawn when you transmit drawn when you transmit

P

I E


T4E06 T4E06 (pg 148)(pg 148)

How many How many amperesamperes are flowing in a circuit are flowing in a circuit when the applied voltage is 120 volts DC when the applied voltage is 120 volts DC and the load is 1200 watts?and the load is 1200 watts?A.A. 20 amperes20 amperes

B.B. 10 amperes10 amperesC.C. 120 amperes120 amperes

D.D. 5 amperes5 amperes

P

I E

I = P / E = 1200 W / 120 V = 10 A


T4C04 T4C04 (pg 148)(pg 148)

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

B.B. CompressorCompressor

C.C. Power SupplyPower SupplyD.D. DemodulatorDemodulator


Metric Prefixes (powers of ten)Metric Prefixes (powers of ten)Prefix Abbrev Power Number

giga- G 109 1,000,000,000

mega- M 106 1,000,000

kilo- K 103 1,000

(basic unit) 100 1

centi- c 10–2 0.01

milli- m 10–3 0.001

micro- 10–6 0.000001

nano- n 10–9 0.000000001

pico- p 10–12 0.000000000001

1——100

1——1000

1————1,000,000


T4E07 T4E07 (pg 149)(pg 149)

How many How many milliamperesmilliamperes is is the same as 1.5 amperes? the same as 1.5 amperes? A.A. 15 milliamperes15 milliamperes

B.B. 150 milliamperes150 milliamperes

C.C. 1500 milliamperes1500 milliamperesD.D. 15000 milliamperes15000 milliamperes

A “milliamp” is A “milliamp” is 11//10001000 amp. amp.

So, each ampere is 1000 milliamps.So, each ampere is 1000 milliamps.

And, thus 1.5 amperes is 1500 milliamps.And, thus 1.5 amperes is 1500 milliamps.


T4E10 T4E10 (pg 149)(pg 149)

How many volts are equal to one How many volts are equal to one microvoltmicrovolt??

A.A. one one-millionth of a voltone one-millionth of a voltB.B. one million voltsone million volts

C.C. one thousand kilovoltsone thousand kilovolts

D.D. one one-thousandth of a voltone one-thousandth of a volt

A A micromicrovolt is volt is 11//1,000,0001,000,000 volt…a volt…a very tinyvery tiny voltage. voltage.


T4E09 T4E09 (pg 149)(pg 149)

How many volts are equal to one How many volts are equal to one kilovoltkilovolt??A.A. one one-thousandth of a voltone one-thousandth of a volt

B.B. one hundred voltsone hundred volts

C.C. one thousand voltsone thousand voltsD.D. one million voltsone million volts

One One kilokilovolt is 1000 volts. volt is 1000 volts.

Remember the prefix “kilo” stands for a thousand.Remember the prefix “kilo” stands for a thousand.


T4E11 T4E11 (pg 149)(pg 149)

How many watts does a hand-held How many watts does a hand-held transceiver put out if the output power transceiver put out if the output power is 500 milliwatts?is 500 milliwatts?A.A. 0.02 watts0.02 watts

B.B. 0.5 watts0.5 wattsC.C. 5 watts5 watts

D.D. 50 watts50 watts

A milliwatt is A milliwatt is 11//10001000 watt. watt.

So, 500 milliwatts = So, 500 milliwatts = 500500//10001000 watt = 0.5 watt. watt = 0.5 watt.

Technician License Class Gordon West Technician Class Manual Pages 142-149 Volts & Amps Presented by...

Documents

Transcript of Technician License Class Gordon West Technician Class Manual Pages 142-149 Volts & Amps Presented by...