Basics Electricity.
Subel. L02
60 questions
L02
Hide Distractors
- L01 33 questions
- L02 60 questions
- L03a 43 questions
- L03b 6 questions
- L04 47 questions
- L05 68 questions
- L06a 11 questions
- L06b 60 questions
- L07 52 questions
- L08 79 questions
- L09a 17 questions
- L09b 44 questions
- L10 54 questions
- L11 87 questions
- L12 32 questions
- L13 55 questions
- L14a 27 questions
- L14b 11 questions
- L15 87 questions
- L16 99 questions
Subelement L02
Section L02
How much voltage does a standard automobile battery usually supply?
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About 120 volts
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About 9 volts
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Correct AnswerAbout 12 volts
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About 240 volts
Which component has a positive and a negative side?
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Correct AnswerA battery
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A potentiometer
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A fuse
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A resistor
Fuses, resistors and potentiometers are not 'polarized' (current can flow through them either way). The battery, however, has a positive terminal and a negative terminal.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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A cell, that can be repeatedly recharged by supplying it with electrical energy, is known as a:
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low leakage cell
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memory cell
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primary cell
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Correct Answerstorage cell
A 'storage cell' can be recharged repeatedly. A 'primary cell', such as a common Zinc-Carbon flashlight cell, can only be used once.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Which of the following is a source of electromotive force (EMF)?
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carbon resistor
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Correct Answerlithium-ion battery
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germanium diode
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P channel FET
An important difference between a conventional flashlight battery and a lead acid battery is that only the lead acid battery:
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has two terminals
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can be completely discharged
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contains an electrolyte
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Correct Answercan be repeatedly recharged
The 'conventional' Zinc-Carbon or Alkaline flashlight battery CANNOT be recharged while a 'storage cell' like a car battery can be recharged numerous times.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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An alkaline cell has a nominal voltage of 1.5 volts. When supplying a great deal of current, the voltage may drop to 1.2 volts. This is caused by the cell's:
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voltage capacity
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Correct Answerinternal resistance
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electrolyte becoming dry
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current capacity
An ideal battery would supply precisely the same voltage regardless of the current drawn. Real-life batteries exhibit 'internal resistance' which causes a drop in voltage when current is drawn. Ever noticed the headlights dim when the starter is cranked on a cold winter day ?
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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An inexpensive primary cell in use today is the carbon-zinc or flashlight cell. This type of cell can be recharged:
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Correct Answernever
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twice
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many times
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once
The 'conventional' Zinc-Carbon or Alkaline flashlight battery CANNOT be recharged while a 'storage cell' like a car battery can be recharged numerous times.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Battery capacity is commonly stated as a value of current delivered over a specified period of time. What is the effect of exceeding that specified current?
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The battery will accept the subsequent charge in shorter time
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The voltage delivered will be higher
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Correct AnswerA battery charge will not last as long
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The internal resistance of the cell is short-circuited
One important specification of rechargeable batteries is the 'capacity' expressed in milliampere-hour (or ampere-hour), a certain amount of current that can be delivered for a given period of time (typically, 20 hours). Exceeding the capacity reduces operating time, the battery is depleted more rapidly.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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To increase the current capacity of a cell, several cells should be connected in:
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Correct Answerparallel
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series
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parallel resonant
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series resonant
To increase the voltage output, several cells are connected in:
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parallel
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series-parallel
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resonance
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Correct Answerseries
key word: VOLTAGE. Adding cells in series brings up the available voltage. However, the total current available from the string remains limited to what a single cell can supply.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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A lithium-ion battery should never be:
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left disconnected
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left overnight at room temperature
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Correct Answershort-circuited
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recharged
How do you find a resistor's tolerance rating?
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By using Thevenin's theorem for resistors
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By reading its Baudot code
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By using a voltmeter
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Correct AnswerBy reading the resistor's colour code
The last band in a resistor's colour code identifies 'tolerance': an allowed variance in percentage from the nominal value. For example, a GOLD band means 5%.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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What do the first three-colour bands on a resistor indicate?
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The resistance material
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The power rating in watts
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The resistance tolerance in percent
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Correct AnswerThe value of the resistor in ohms
What would the fourth colour band on a 47 ohm resistor indicate?
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Correct AnswerThe resistance tolerance in percent
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The value of the resistor in ohms
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The power rating in watts
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The resistance material
The last band in a resistor's colour code identifies 'tolerance': an allowed variance in percentage from the nominal value. For example, a GOLD band means 5%.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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What are the possible values of a 100 ohm resistor with a 10% tolerance?
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Correct Answer90 to 110 ohms
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90 to 100 ohms
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10 to 100 ohms
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80 to 120 ohms
How do you find a resistor's value?
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By using the Baudot code
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Correct AnswerBy using the resistor's colour code
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By using a voltmeter
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By using Thevenin's theorem for resistors
A club project requires that a resistive voltage divider provide a very accurate and predictable ratio. Out of the list below, which resistor tolerance would you select?
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10%
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20%
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Correct Answer0.1%
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5%
Key words: ACCURATE and PREDICTABLE. The smallest possible "tolerance" will ensure that the actual value of the resistors fall within a narrow range of their nominal values.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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You need a current limiting resistor for a light-emitting diode (LED). The actual resistance is not critical at all. Out of the list below, which resistor tolerance would you select?
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10%
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Correct Answer20%
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0.1%
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5%
Key words: NOT CRITICAL. A wide tolerance is amply acceptable when the actual value of the resistor is not critical. The extra cost of a precision resistor is not needed.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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If a carbon resistor's temperature is increased, what will happen to the resistance?
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It will stay the same
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It will become time dependent
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It will increase by 20% for every 10 degrees centigrade
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Correct AnswerIt will change depending on the resistor's temperature coefficient rating
Which colour band would differentiate a 120-ohm from a 1200-ohm resistor?
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Second band
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Fourth band
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Correct AnswerThird band
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First band
The first two bands are significant digits, the third band is a multiplier. The fourth band is tolerance. In this example, both first bands read '1', both second bands read '2'. The third band multiplies by 10 or 100 as the case may be.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Given that red=2, violet=7 and yellow=4, what is the nominal value of a resistor whose colour code reads "red", "violet" and "yellow"?
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Correct Answer270 kilohms
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274 ohms
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72 kilohms
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27 megohms
The first two bands are significant digits, the third band is a multiplier. The fourth band is tolerance. In this example, the first two digits are '27' and the multiplier adds four zeroes (or multiplies by 10 000). Result = 270 000 ohms or 270 kilohms.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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If an ammeter marked in amperes is used to measure a 3000 milliampere current, what reading would it show?
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3 000 000 amperes
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Correct Answer3 amperes
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0.003 ampere
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0.3 ampere
Milli is a thousandth. A thousand milliamperes is one ampere. Converting from milliamperes to amperes: from small units to larger units, requires fewer digits, decimal point moves to the left by three positions, a thousand times less.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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If a voltmeter marked in volts is used to measure a 3500 millivolt potential, what reading would it show?
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Correct Answer3.5 volts
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0.35 volt
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35 volts
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350 volts
Milli is a thousandth. A thousand millivolts is one volt. Converting from millivolts to volts: from small units to larger units, requires fewer digits, decimal point moves to the left by three positions, a thousand times less.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Kilohm is a thousand ohms. Converting from kilohm to ohms: from large units to smaller units, requires more digits, decimal point moves to the right by three positions, a thousand times more.
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Kilovolt is a thousand volts. Converting from kilovolts to volts: from large units to smaller units, requires more digits, decimal point moves to the right by three positions, a thousand times more.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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A current of one quarter ampere may be written as:
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0.25 milliampere
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250 microamperes
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Correct Answer250 milliamperes
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0.5 amperes
One quarter ampere is 0.25 amperes. Milli is one thousandth. One ampere is a thousand milliamperes. Converting from ampere to milliampere: from large units to smaller units, requires more digits, decimal point moves to the right by three positions, a thousand times more.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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A millivolt is a thousandth of a volt. A volt is one thousand millivolts. Converting from volts to millivolts: from large units to smaller units, requires more digits, decimal point moves to the right by three positions, a thousand times more.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Name three good electrical conductors.
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Copper, aluminum, paper
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Copper, gold, mica
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Correct AnswerGold, silver, aluminum
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Gold, silver, wood
Wood, paper and mica do NOT conduct electricity. The best conductors, in descending order, are: Silver, Copper, Gold and Aluminum.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Name four good electrical insulators.
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Plastic, rubber, wood, carbon
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Paper, glass, air, aluminum
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Glass, wood, copper, porcelain
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Correct AnswerGlass, air, plastic, porcelain
Why do resistors sometimes get hot when in use?
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Correct AnswerSome electrical energy passing through them is lost as heat
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Their reactance makes them heat up
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Hotter circuit components nearby heat them up
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They absorb magnetic energy which makes them hot
Power is voltage times current, P = E * I. When current flows through a resistor, a 'voltage drop' ensues. Volts times amperes become watts. Power is dissipated as heat.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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What is the best conductor among the following materials?
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silicon
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aluminium
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Correct Answercopper
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carbon
The best conductors, in descending order, are: Silver, Copper, Gold and Aluminum. Carbon is a poor conductor, it is used to fabricate resistors. Silicon is used to make 'semiconductors'.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Which type of material listed will most readily allow an electric current to flow?
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a dielectric
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Correct Answera conductor
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an insulator
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a semiconductor
As the name implies, a 'conductor' readily passes electrical current. An Insulator ( synonym = dielectric ) does not let current flow. A resistor conducts but badly.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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A length of metal is connected in a circuit and is found to conduct electricity very well. It would be best described as having a:
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high wattage
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low wattage
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Correct Answerlow resistance
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high resistance
Reciprocal = 'the inverse of something'. 1 over resistance yields CONDUCTANCE. Low resistance implies high conductance. High resistance implies little conductance.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Voltage drop means:
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Correct Answerthe voltage developed across the terminals of a component
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any point in a radio circuit which has zero voltage
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the difference in voltage at output terminals of a transformer
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the voltage which is dissipated before useful work is accomplished
As current flows through electronic components, some voltage is 'lost'. Remember voltage as 'pressure', there is more 'pressure' before a resistor than after it: this represents a 'voltage drop'.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Which electrical circuit will have no current?
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A complete circuit
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A closed circuit
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Correct AnswerAn open circuit
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A short circuit
'Open' circuit = no current ( a loop from one side of the voltage source to the other side does NOT exist, the loop is open ). 'Closed' circuit = current ( a path exists from one side of the voltage source to the other side, current flows, the loop is closed ). 'Short circuit' = heavy current ( a very low resistance path exists between from one side of the voltage source to the other side, large current ensues ).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Which electrical circuit draws too much current?
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A closed circuit
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An open circuit
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Correct AnswerA short circuit
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A dead circuit
'Open' circuit = no current ( a loop from one side of the voltage source to the other side does NOT exist, the loop is open ). 'Closed' circuit = current ( a path exists from one side of the voltage source to the other side, current flows, the loop is closed ). 'Short circuit' = heavy current ( a very low resistance path exists between from one side of the voltage source to the other side, large current ensues ).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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What term means the number of times per second that an alternating current flows back and forth?
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Pulse rate
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Inductance
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Correct AnswerFrequency
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Speed
Frequency is the number of cycles per second of an Alternating Current (AC). Frequency is expressed in hertz (Hz). One hertz is one cycle per second.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Approximately what frequency range can most humans hear?
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0 - 20 Hz
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Correct Answer20 - 20 000 Hz
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20 000 - 30 000 Hz
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200 - 200 000 Hz
Hz = hertz = cycles per second. Frequencies audible to humans range from 20 Hz to 20 000 Hz. Speech frequencies important for intelligibility in communications range from 300 Hz to 3000 Hz.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Why do we call signals in the range 20 Hz to 20 000 Hz audio frequencies?
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Because the human ear cannot sense anything in this range
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Because this range is too low for radio energy
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Because the human ear can sense radio waves in this range
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Correct AnswerBecause the human ear can sense sounds in this range
Hz = hertz = cycles per second. Frequencies audible to humans range from 20 Hz to 20 000 Hz. Speech frequencies important for intelligibility in communications range from 300 Hz to 3000 Hz.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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What does 60 hertz (Hz) mean?
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Correct Answer60 cycles per second
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6000 metres per second
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60 metres per second
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6000 cycles per second
Hz = hertz = cycles per second. Frequency is the number of cycles per second of an Alternating Current (AC). Frequency is expressed in hertz (Hz). One hertz is one cycle per second.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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If the frequency of the waveform is 100 Hz, the time for one cycle is:
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Correct Answer0.01 second
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10 seconds
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0.0001 second
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1 second
100 Hz = 100 hertz = 100 cycles per second. The duration of ONE cycle, the "period", is 1 / frequency. In this example, 1 / 100 Hz yields 0.01 second.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Current in an AC circuit goes through a complete cycle in 0.1 second. This means the AC has a frequency of:
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1 Hz
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100 Hz
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1000 Hz
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Correct Answer10 Hz
One cycle in 0.1 second, how many cycles in a second ? The duration of ONE cycle, the "period", and frequency have an inverse relation: Frequency is 1 / period. In this example, 1 / 0.1 second yields 10 hertz.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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A signal is composed of a fundamental frequency of 2 kHz and another of 4 kHz. This 4 kHz signal is referred to as:
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a fundamental of the 2 kHz signal
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the DC component of the main signal
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a dielectric signal of the main signal
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Correct Answera harmonic of the 2 kHz signal
'Harmonics' are integer MULTIPLES (e.g., 2x, 3x, 4x, 5x,...) of a given frequency. The base frequency is referred to as the 'fundamental'.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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A force of repulsion exists between two _________ magnetic poles.
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unlike
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positive
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negative
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Correct Answerlike
How is a voltmeter usually connected to a circuit under test?
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In quadrature with the circuit
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In phase with the circuit
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Correct AnswerIn parallel with the circuit
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In series with the circuit
key word: VOLTMETER. An instrument to measure voltage. The voltmeter is always connected in parallel to measure a difference of potential between two points, across a component, etc.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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How is an ammeter usually connected to a circuit under test?
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In quadrature with the circuit
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In phase with the circuit
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In parallel with the circuit
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Correct AnswerIn series with the circuit
key word: AMMETER. Ammeter comes from the words ampere + meter, it is used to measure current. Current flows THROUGH a circuit. The circuit must be 'broken' and the ammeter inserted in series with the circuit to measure current. Ammeters have very low resistance and, thus, have little effect once inserted in the circuit.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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What does a multimeter measure?
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Correct AnswerVoltage, current and resistance
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Resistance, capacitance and inductance
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Resistance and reactance
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SWR and power
The correct instrument to measure plate current or collector current of a transmitter is:
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a voltmeter
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Correct Answeran ammeter
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an ohmmeter
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a wattmeter
Which of the following meters would you use to measure the power supply current drawn by a small hand-held transistorized receiver?
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An electrostatic voltmeter
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Correct AnswerA DC ammeter
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An RF ammeter
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An RF power meter
When measuring current drawn from a DC power supply, it is true to say that the meter will act in circuit as:
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an extra current drain
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an insulator
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Correct Answera low value resistance
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a perfect conductor
This is a bit of a catch. A PERFECT conductor would exhibit ZERO resistance. An ammeter actually has a very low resistance. [ For example, a 10 A ammeter can have a resistance of 0.005 ohms, a 1 A ammeter can have 0.05 ohms and a 500 mA ammeter can introduce 0.2 ohms of resistance in the circuit. ]
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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When measuring the current drawn by a receiver from a power supply, the current meter should be placed:
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in parallel with one of the receiver power leads
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Correct Answerin series with one of the receiver power leads
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in series with both receiver power leads
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in parallel with both receiver power supply leads
Ammeter comes from the words ampere + meter, it is used to measure current. Current flows THROUGH a circuit. The circuit must be 'broken' and the ammeter inserted in series with the circuit to measure current. Ammeters have very low resistance and, thus, have little effect once inserted in the circuit.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Potential difference is measured by means of:
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Correct Answera voltmeter
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a wattmeter
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an ohmmeter
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an ammeter
The instrument used for measuring the flow of electrical current is the:
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wattmeter
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voltmeter
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Correct Answerammeter
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faradmeter
Ammeter comes from the words ampere + meter, it is used to measure current. Current flow THROUGH a circuit. The circuit must be 'broken' and the ammeter inserted in series with the circuit to measure current. Ammeters have very low resistance and, thus, have little effect once inserted in the circuit.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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In measuring volts and amperes, the connections should be made with:
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Correct Answerthe voltmeter in parallel and ammeter in series
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the voltmeter in series and ammeter in parallel
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both voltmeter and ammeter in series
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both voltmeter and ammeter in parallel
The voltmeter is always connected in parallel to measure a difference of potential between two points, across a component, etc. Ammeter comes from the words Ampere + meter, it is used to measure current. Current flow THROUGH a circuit. The circuit must be 'broken' and the ammeter inserted in series with the circuit to measure current. Ammeters have very low resistance and, thus, have little effect once inserted in the circuit.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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