All 50 Ham Radio Technician questions for T5 Electrical Principles with the correct answers marked and a short explanation for each, from the official 2026-2030 question pool. Test yourself with the free practice exam.
T5A01
Electrical current is measured in which of the following units?
A. Volts
B. Watts
C. Ohms
D. Amperes ✓
Why: Current, the flow of electric charge, is measured in amperes (amps). Volts measure electromotive force, watts measure power, and ohms measure resistance.
T5A02
Electrical power is measured in which of the following units?
A. Volts
B. Watts ✓
C. Watt-hours
D. Amperes
Why: Electrical power, the rate of using energy, is measured in watts. Watt-hours measure energy used over time, not power itself.
T5A03
What is the term for the flow of electrons in an electric circuit?
A. Voltage
B. Amperes per second
C. Volts per second
D. Current ✓
Why: Current is the flow of electrons through a circuit, measured in amperes. Voltage is the electrical pressure that pushes the current.
T5A04
What term describes the number of times per second that an alternating current makes a complete cycle?
A. Pulse rate
B. Wave number
C. Frequency ✓
D. Wavelength
Why: Frequency is the number of complete cycles per second of an alternating current, measured in hertz. Wavelength is the distance one cycle travels.
T5A05
A difference in which of the following causes electron flow?
A. Voltage ✓
B. Ampere-hours
C. Capacitance
D. Inductance
Why: A voltage difference (potential difference) between two points pushes electrons to flow from one point to the other, similar to how water pressure causes water to flow.
T5A06
What is the unit of frequency?
A. Hertz ✓
B. Henry
C. Farad
D. Epicycles per second
Why: Frequency is measured in hertz (Hz), equal to one cycle per second. The henry is the unit of inductance and the farad is the unit of capacitance.
T5A07
Why are metals generally good conductors of electricity?
A. They have relatively high density
B. They have many free electrons ✓
C. They have many free protons
D. They have relatively high Young’s modulus values
Why: Metals have many loosely held free electrons that can move easily from atom to atom, allowing current to flow with little resistance. Protons are fixed in atomic nuclei and do not carry current.
T5A08
Which of the following is a good electrical insulator?
A. Sea water
B. Glass ✓
C. Stainless steel
D. Graphite
Why: Glass has very few free electrons, so it resists current flow and is used for insulators. Sea water, stainless steel and graphite all conduct electricity.
T5A09
Which of the following describes alternating current?
A. Current that alternates between a positive direction and zero
B. Current that alternates between a negative direction and zero
C. Current that alternates between positive and negative directions ✓
D. All these answers are correct
Why: Alternating current periodically reverses direction, flowing first in one direction (positive) and then in the opposite direction (negative), such as the 60 Hz power in a household outlet.
T5A10
Which term describes the rate at which electrical energy is used?
A. Resistance
B. Current
C. Power ✓
D. Voltage
Why: Power is the rate at which electrical energy is used or delivered, measured in watts. One watt equals one joule of energy per second.
T5A11
What type of current flow is opposed by resistance?
A. Direct current
B. Alternating current
C. RF current
D. All these choices are correct ✓
Why: Resistance opposes the flow of any kind of current, whether direct current, alternating current, or RF current, and it converts some of that energy to heat. All three answers apply.
T5B01
How many milliamperes is 1.5 amperes?
A. 0.0000015 milliamperes
B. 0.0015 milliamperes
C. 1500 milliamperes ✓
D. 1,500,000 milliamperes
Why: The prefix milli means one-thousandth, so 1 ampere equals 1000 milliamperes. To convert amperes to milliamperes, multiply by 1000: 1.5 A x 1000 = 1500 mA.
T5B02
Which is equal to 1,500,000 hertz?
A. 1500 kHz ✓
B. 1500 MHz
C. 15 GHz
D. 150 kHz
Why: One kilohertz is 1000 hertz, so divide by 1000 to convert: 1,500,000 Hz / 1000 = 1500 kHz. The same value also equals 1.5 MHz, but not 1500 MHz.
T5B03
Which is equal to one kilovolt?
A. One one-thousandth of a volt
B. One hundred volts
C. One thousand volts ✓
D. One million volts
Why: The metric prefix kilo means one thousand, so one kilovolt (kV) equals 1000 volts. One one-thousandth of a volt would be a millivolt, and one million volts a megavolt.
T5B04
Which is equal to one microvolt?
A. One one-millionth of a volt ✓
B. One million volts
C. One thousand kilovolts
D. One one-thousandth of a volt
Why: The metric prefix micro means one-millionth, so one microvolt equals 0.000001 volt. One one-thousandth of a volt is a millivolt. Receiver sensitivity is often stated in microvolts.
T5B05
Which is equal to 500 milliwatts?
A. 5 watts
B. 0.5 watts ✓
C. 500,000 watts
D. 500,000,000 watts
Why: The prefix milli means one-thousandth, so convert milliwatts to watts by dividing by 1000: 500 mW / 1000 = 0.5 watts, or half a watt.
T5B06
Which is equal to 3000 milliamperes?
A. 0.003 amperes
B. 0.3 amperes
C. 3,000,000 amperes
D. 3 amperes ✓
Why: There are 1000 milliamperes in one ampere, so convert by dividing by 1000: 3000 mA / 1000 = 3 amperes. Multiplying instead would give the wrong answer of 3,000,000.
T5B07
Which is equal to 3.525 MHz?
A. 0.003525 kHz
B. 35.25 kHz
C. 3525 kHz ✓
D. 3,525,000 kHz
Why: One megahertz equals 1000 kilohertz, so to convert MHz to kHz, multiply by 1000: 3.525 MHz x 1000 = 3525 kHz. This frequency is in the 80-meter band.
T5B08
Which is equal to 1,000,000 picofarads?
A. 0.001 microfarads
B. 1 microfarad ✓
C. 1000 microfarads
D. 1,000,000,000 microfarads
Why: Pico means one-trillionth and micro means one-millionth, so one microfarad equals 1,000,000 picofarads. Therefore 1,000,000 pF is exactly 1 microfarad.
T5B09
Which decibel value most closely represents a power increase from 5 watts to 10 watts?
A. 2 dB
B. 3 dB ✓
C. 5 dB
D. 10 dB
Why: dB = 10 log (P2/P1). Going from 5 to 10 watts doubles the power: 10 log(2) is about 3 dB. Remember that each doubling is roughly +3 dB.
T5B10
Which decibel value most closely represents a power decrease from 12 watts to 3 watts?
A. -1 dB
B. -3 dB
C. -6 dB ✓
D. -9 dB
Why: dB = 10 log (3/12) = 10 log (0.25), which is about -6 dB. Halving power is -3 dB, and 12 to 3 watts is halving twice, so -3 + -3 = -6 dB.
T5B11
Which decibel value represents a power increase from 20 watts to 200 watts?
A. 10 dB ✓
B. 12 dB
C. 18 dB
D. 28 dB
Why: dB = 10 log (200/20) = 10 log(10) = 10 dB. A tenfold increase in power is always 10 dB.
T5B12
Which is equal to 28400 kHz?
A. 28.400 kHz
B. 2.800 MHz
C. 284.00 MHz
D. 28.400 MHz ✓
Why: Since 1000 kHz equals 1 MHz, convert by dividing by 1000: 28400 kHz / 1000 = 28.400 MHz. This frequency is in the Technician phone segment of 10 meters.
T5B13
Which is equal to 2425 MHz?
A. 0.002425 GHz
B. 24.25 GHz
C. 2.425 GHz ✓
D. 242.5 GHz
Why: Since 1000 MHz equals 1 GHz, convert by dividing by 1000: 2425 MHz / 1000 = 2.425 GHz. This frequency is in the 13-centimeter amateur band.
T5C01
What describes the ability to store energy in an electric field?
A. Inductance
B. Resistance
C. Frequency
D. Capacitance ✓
Why: Capacitance is the ability to store energy in an electric field, such as between the plates of a capacitor. Inductance stores energy in a magnetic field instead.
T5C02
What is the unit of capacitance?
A. Farad ✓
B. Ohm
C. Volt
D. Henry
Why: Capacitance is measured in farads. Practical capacitors are usually rated in microfarads or picofarads because one farad is very large.
T5C03
What describes the ability to store energy in a magnetic field?
A. Admittance
B. Capacitance
C. Resistance
D. Inductance ✓
Why: Inductance is the ability to store energy in a magnetic field, such as the field around a coil carrying current. Capacitance stores energy in an electric field.
T5C04
What is the unit of inductance?
A. Coulomb
B. Farad
C. Henry ✓
D. Ohm
Why: The unit of inductance is the henry, named after Joseph Henry. Small inductors used in radio circuits are often rated in millihenries or microhenries. The farad is the unit of capacitance.
T5C05
What is the unit of impedance?
A. Volt
B. Ampere
C. Coulomb
D. Ohm ✓
Why: Impedance, the total opposition to AC current including resistance and reactance, is measured in ohms, the same unit used for resistance.
T5C06
What is the abbreviation for kilohertz?
A. kHz ✓
B. khz
C. KHz
D. KHZ
Why: The standard abbreviation for kilohertz is kHz: a lowercase k for kilo and Hz (capital H) for hertz, which is named after Heinrich Hertz.
T5C07
What is the abbreviation for megahertz?
A. mHz
B. mHZ
C. Mhz
D. MHz ✓
Why: The standard abbreviation for megahertz is MHz. A capital M means mega (million); a lowercase m would mean milli (thousandth), and hertz is always written Hz.
T5C08
What formula is used to calculate electrical power (P) in a DC circuit?
A. P = I x E ✓
B. P = E / I
C. P = I2 x E
D. P = I / E
Why: In a DC circuit, power equals current times voltage: P = I x E, where E is voltage in volts and I is current in amps. For example, 2 amps at 12 volts delivers 24 watts.
T5C09
How much power is delivered by a voltage of 13.8 volts DC and a current of 10 amperes?
A. 138 watts ✓
B. 0.7 watts
C. 23.8 watts
D. 3.8 watts
Why: DC power equals current times voltage: P = I x E. Here P = 10 amperes x 13.8 volts = 138 watts. Adding the values (23.8) or dividing them gives wrong answers.
T5C10
How much power is delivered by a voltage of 12 volts DC and a current of 2.5 amperes?
A. 4.8 watts
B. 30 watts ✓
C. 14.5 watts
D. 0.208 watts
Why: DC power equals current times voltage: P = I x E. Here P = 2.5 amperes x 12 volts = 30 watts. Dividing the values (4.8) or adding them (14.5) gives wrong answers.
T5C11
How much current is required to deliver 120 watts at a voltage of 12 volts DC?
A. 0.1 amperes
B. 10 amperes ✓
C. 12 amperes
D. 132 amperes
Why: Rearrange the power formula P = I x E to solve for current: I = P / E. So I = 120 watts / 12 volts = 10 amperes. Check: 10 A x 12 V = 120 W.
T5C12
What is impedance?
A. The opposition to AC current flow ✓
B. The inverse of resistance
C. The inverse of reactance
D. The power handling capability of a component
Why: Impedance is the total opposition to AC current flow, combining resistance and reactance, and is measured in ohms. It is not simply the inverse of resistance.
T5D01
What formula is used to calculate current in a circuit?
A. I = E x R
B. I = E / R ✓
C. I = E2 x R
D. I = E2 / R
Why: From Ohm's law, current equals voltage divided by resistance: I = E / R. For example, 12 volts across 6 ohms gives 2 amps.
T5D02
What formula is used to calculate voltage in a circuit?
A. E = I x R ✓
B. E = I / R
C. E = I2 x R
D. E = I2 / R
Why: Ohm's law: voltage equals current times resistance, E = I x R. For example, 2 amps through 5 ohms gives 10 volts.
T5D03
What formula is used to calculate resistance in a circuit?
A. R = E x I
B. R = E / I ✓
C. R = E + I
D. R = E - I
Why: Rearranging Ohm's law gives resistance equals voltage divided by current: R = E / I. For example, 12 volts and 2 amps means 6 ohms.
T5D04
What is the resistance of a circuit in which a current of 3 amperes flows when connected to 90 volts?
A. 3 ohms
B. 30 ohms ✓
C. 1/30 ohm
D. 270 ohms
Why: Use Ohm's law rearranged for resistance: R = E / I. Here R = 90 volts / 3 amperes = 30 ohms. Multiplying instead (270) or inverting (1/30) are the common mistakes.
T5D05
What is the resistance of a circuit for which the applied voltage is 12 volts and the current flow is 1.5 amperes?
A. 18 ohms
B. 0.125 ohms
C. 8 ohms ✓
D. 13.5 ohms
Why: Use Ohm's law rearranged for resistance: R = E / I. Here R = 12 volts / 1.5 amperes = 8 ohms. Note 13.5 just adds the numbers and 18 multiplies them.
T5D06
What is the resistance of a circuit that draws 4 amperes from a 12-volt source?
A. 3 ohms ✓
B. 16 ohms
C. 48 ohms
D. 8 ohms
Why: Use Ohm's law rearranged for resistance: R = E / I. Here R = 12 volts / 4 amperes = 3 ohms. Multiplying the values (48) gives power in watts, not resistance.
T5D07
What is the current in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms?
A. 9600 amperes
B. 200 amperes
C. 0.667 amperes
D. 1.5 amperes ✓
Why: Use Ohm's law for current: I = E / R. Here I = 120 volts / 80 ohms = 1.5 amperes. Dividing the other way (80 / 120 = 0.667) is a common error.
T5D08
What is the current through a 100-ohm resistor connected across 200 volts?
A. 20,000 amperes
B. 0.5 amperes
C. 2 amperes ✓
D. 100 amperes
Why: Use Ohm's law for current: I = E / R. Here I = 200 volts / 100 ohms = 2 amperes. Dividing resistance by voltage (0.5) or multiplying (20,000) are the wrong choices.
T5D09
What is the current through a 24-ohm resistor connected across 240 volts?
A. 2400 amperes
B. 0.1 amperes
C. 10 amperes ✓
D. 5760 amperes
Why: Use Ohm's law for current: I = E / R. Here I = 240 volts / 24 ohms = 10 amperes. Dividing resistance by voltage gives the wrong answer of 0.1.
T5D10
What is the voltage across a 2-ohm resistor if a current of 0.5 amperes flows through it?
A. 1 volt ✓
B. 0.25 volts
C. 2.5 volts
D. 1.5 volts
Why: Use Ohm's law for voltage: E = I x R. Here E = 0.5 amperes x 2 ohms = 1 volt. Adding the numbers (2.5) or dividing them (0.25) gives a wrong result.
T5D11
What is the voltage across a 10-ohm resistor if a current of 1 ampere flows through it?
A. 1 volt
B. 10 volts ✓
C. 11 volts
D. 9 volts
Why: Use Ohm's law for voltage: E = I x R. Here E = 1 ampere x 10 ohms = 10 volts. Adding (11) or subtracting (9) the values is not how Ohm's law works.
T5D12
What is the voltage across a 10-ohm resistor if a current of 2 amperes flows through it?
A. 8 volts
B. 0.2 volts
C. 12 volts
D. 20 volts ✓
Why: Use Ohm's law for voltage: E = I x R. Here E = 2 amperes x 10 ohms = 20 volts. Adding (12), subtracting (8) or dividing (0.2) the values gives wrong answers.
T5D13
In which type of circuit is the current always the same through all components?
A. Series ✓
B. Parallel
C. Resonant
D. Branch
Why: In a series circuit there is only one path for current, so the same current flows through every component. The voltage divides among the components.
T5D14
In which type of circuit is the voltage always the same across all components?
A. Series
B. Parallel ✓
C. Resonant
D. Branch
Why: In a parallel circuit, every component connects across the same two points, so each has the same voltage across it. The current divides among the branches.