Electrical current is measured in which of the following units?
AnswerAmperes
Electrical current is the rate of electric charge flow. Its standard unit is the ampere, usually shortened to amp.
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T5 · Electrical Principles
Technician · correct answers only, in question-pool order.
Electrical power is measured in which of the following units?
AnswerWatts
Electrical power describes how quickly electrical energy is being used or delivered. The standard unit of power is the watt.
What is the term for the flow of electrons in an electric circuit?
AnswerCurrent
The movement of electric charge through a circuit is called current. In ordinary conductors, that charge flow is associated with moving electrons.
What term describes the number of times per second that an alternating current makes a complete cycle?
AnswerFrequency
Frequency tells how many complete cycles occur each second. For alternating current, each complete positive-and-negative cycle counts once.
A difference in which of the following causes electron flow?
AnswerVoltage
A voltage difference creates the electric potential that can drive electrons through a conductive path.
What is the unit of frequency?
AnswerHertz
Frequency is measured in hertz. One hertz means one complete cycle per second.
Why are metals generally good conductors of electricity?
AnswerThey have many free electrons
Metals contain many electrons that are free to move through the material. Those mobile charge carriers make metals good electrical conductors.
Which of the following is a good electrical insulator?
AnswerGlass
Glass has very few free charge carriers, so it strongly resists electric current and is commonly used as an insulating material.
Which of the following describes alternating current?
AnswerCurrent that alternates between positive and negative directions
Alternating current repeatedly reverses direction. During each cycle, current flows one way and then the opposite way.
Which term describes the rate at which electrical energy is used?
AnswerPower
Power is the rate at which energy is transferred or used. More power means more energy is being used per unit time.
What type of current flow is opposed by resistance?
AnswerDirect current, alternating current, and RF current.
Resistance opposes current flow regardless of whether the current is direct, alternating, or at radio frequency.
How many milliamperes is 1.5 amperes?
Answer1500 milliamperes
The prefix milli means one-thousandth. Therefore one ampere equals 1000 milliamperes, so 1.5 amperes equals 1500 milliamperes.
Which is equal to 1,500,000 hertz?
Answer1500 kHz
One kilohertz is 1000 hertz. Dividing 1,500,000 hertz by 1000 gives 1500 kilohertz.
Which is equal to one kilovolt?
AnswerOne thousand volts
The prefix kilo means one thousand. One kilovolt is therefore 1000 volts.
Which is equal to one microvolt?
AnswerOne one-millionth of a volt
The prefix micro means one-millionth, or 10⁻⁶. One microvolt is one one-millionth of a volt.
Which is equal to 500 milliwatts?
Answer0.5 watts
One watt contains 1000 milliwatts. Dividing 500 milliwatts by 1000 gives 0.5 watt.
Which is equal to 3000 milliamperes?
Answer3 amperes
One ampere equals 1000 milliamperes. Therefore 3000 milliamperes equals 3 amperes.
Which is equal to 3.525 MHz?
Answer3525 kHz
One megahertz equals 1000 kilohertz. Multiplying 3.525 MHz by 1000 gives 3525 kHz.
Which is equal to 1,000,000 picofarads?
Answer1 microfarad
One microfarad equals one million picofarads. Therefore 1,000,000 pF is exactly 1 µF.
Which decibel value most closely represents a power increase from 5 watts to 10 watts?
Answer3 dB
A doubling of power is approximately a 3 dB increase. Going from 5 watts to 10 watts doubles the power.
Which decibel value most closely represents a power decrease from 12 watts to 3 watts?
Answer-6 dB
Dropping from 12 watts to 3 watts reduces power to one quarter. Each halving is about -3 dB, so two halvings are about -6 dB.
Which decibel value represents a power increase from 20 watts to 200 watts?
Answer10 dB
Going from 20 watts to 200 watts multiplies power by ten. A tenfold power increase is 10 dB.
Which is equal to 28400 kHz?
Answer28.400 MHz
One megahertz equals 1000 kilohertz. Dividing 28,400 kHz by 1000 gives 28.400 MHz.
Which is equal to 2425 MHz?
Answer2.425 GHz
One gigahertz equals 1000 megahertz. Dividing 2425 MHz by 1000 gives 2.425 GHz.
What describes the ability to store energy in an electric field?
AnswerCapacitance
Capacitance is the ability of a component or circuit to store energy in an electric field.
What is the unit of capacitance?
AnswerFarad
The standard unit of capacitance is the farad, named for Michael Faraday.
What describes the ability to store energy in a magnetic field?
AnswerInductance
Inductance is associated with energy stored in a magnetic field, typically around a coil or other current-carrying conductor.
What is the unit of impedance?
AnswerOhm
Impedance is the opposition a circuit presents to alternating current. Like resistance, impedance is measured in ohms.
What is the abbreviation for kilohertz?
AnswerkHz
The standard abbreviation for kilohertz uses a lowercase k, uppercase H, and lowercase z: kHz.
What is the abbreviation for megahertz?
AnswerMHz
The standard abbreviation for megahertz uses uppercase M and H with lowercase z: MHz.
What formula is used to calculate electrical power (P) in a DC circuit?
AnswerP = I x E
DC electrical power equals voltage multiplied by current. In the question-pool notation, E represents voltage and I represents current.
How much power is delivered by a voltage of 13.8 volts DC and a current of 10 amperes?
Answer138 watts
Use P = E × I. Multiplying 13.8 volts by 10 amperes gives 138 watts.
How much power is delivered by a voltage of 12 volts DC and a current of 2.5 amperes?
Answer30 watts
Use P = E × I. Multiplying 12 volts by 2.5 amperes gives 30 watts.
How much current is required to deliver 120 watts at a voltage of 12 volts DC?
Answer10 amperes
Rearrange P = E × I to I = P ÷ E. Dividing 120 watts by 12 volts gives 10 amperes.
What is impedance?
AnswerThe opposition to AC current flow
Impedance is the total opposition a circuit presents to alternating current, including resistance and frequency-dependent effects.
What formula is used to calculate current in a circuit?
AnswerI = E / R
Ohm's Law relates voltage, current, and resistance. Solving E = I × R for current gives I = E ÷ R.
What formula is used to calculate voltage in a circuit?
AnswerE = I x R
Ohm's Law states that voltage equals current multiplied by resistance.
What formula is used to calculate resistance in a circuit?
AnswerR = E / I
Starting with E = I × R and solving for resistance gives R = E ÷ I.
What is the resistance of a circuit in which a current of 3 amperes flows when connected to 90 volts?
Answer30 ohms
Use R = E ÷ I. Dividing 90 volts by 3 amperes gives 30 ohms.
What is the resistance of a circuit for which the applied voltage is 12 volts and the current flow is 1.5 amperes?
Answer8 ohms
Use R = E ÷ I. Dividing 12 volts by 1.5 amperes gives 8 ohms.
What is the resistance of a circuit that draws 4 amperes from a 12-volt source?
Answer3 ohms
Use R = E ÷ I. Dividing 12 volts by 4 amperes gives 3 ohms.
What is the current in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms?
Answer1.5 amperes
Use I = E ÷ R. Dividing 120 volts by 80 ohms gives 1.5 amperes.
What is the current through a 100-ohm resistor connected across 200 volts?
Answer2 amperes
Use I = E ÷ R. Dividing 200 volts by 100 ohms gives 2 amperes.
What is the current through a 24-ohm resistor connected across 240 volts?
Answer10 amperes
Use I = E ÷ R. Dividing 240 volts by 24 ohms gives 10 amperes.
What is the voltage across a 2-ohm resistor if a current of 0.5 amperes flows through it?
Answer1 volt
Use E = I × R. Multiplying 0.5 ampere by 2 ohms gives 1 volt.
What is the voltage across a 10-ohm resistor if a current of 1 ampere flows through it?
Answer10 volts
Use E = I × R. One ampere through 10 ohms produces a voltage drop of 10 volts.
What is the voltage across a 10-ohm resistor if a current of 2 amperes flows through it?
Answer20 volts
Use E = I × R. Two amperes through 10 ohms produces a voltage drop of 20 volts.
In which type of circuit is the current always the same through all components?
AnswerSeries
A series circuit has only one path for current. Because every component lies in that same path, the same current flows through each one.
In which type of circuit is the voltage always the same across all components?
AnswerParallel
Components connected in parallel share the same two circuit nodes, so the voltage across every parallel branch is the same.