Question of the Week - Answer 230313https://learnemc.com/qotw-230313

EMC Question of the Week: March 13, 2023 An LC low-pass filter is designed to attenuate noise from a 5-Ω source before it reaches a 500-Ω load. In order to avoid a resonance (negative insertion loss) near the cut-off frequency, the values of L and C...

Question of the Week - Answer 171030https://learnemc.com/qotw-171030

EMC Question of the Week: October 30, 2017 The best component to use to control the transition times of a digital signal in a CMOS circuit is a, resistor capacitor inductor ferrite Answer The correct answer is "a". When driving capacitive CMOS loads,...

Question of the Week - Answer 200727https://learnemc.com/qotw-200727

EMC Question of the Week: July 27, 2020 What is the wavelength of a 300 MHz electromagnetic plane wave that is represented using phasor notation as, E → = 10 e − j 3 π x y ^ V/m 0.67 meters 1.0 meters 1.5 meters not enough information Answer The...

Question of the Week - Answer 201012https://learnemc.com/qotw-201012

EMC Question of the Week: October 12, 2020 Which EM coupling mechanism is proportional to the source voltage, rather than the source current? common-impedance coupling electric-field coupling magnetic-field coupling radiated coupling Answer The best...

Question of the Week - Answer 230515https://learnemc.com/qotw-230515

EMC Question of the Week: May 15, 2023 A linear dipole antenna is driven by a 100-MHz sinusoidal source. At all points in free space, the electric and magnetic fields generated by the source must be in phase be 90o out-of-phase be perpendicular have a...

Question of the Week - Answer 230814https://learnemc.com/qotw-230814

EMC Question of the Week: August 14, 2023 Controlled impedance traces on printed circuit boards typically have a 50-Ω characteristic impedance. Traces without a controlled impedance are more likely to have a characteristic impedance of around 70-80 Ω....

Question of the Week - Answer 220124https://learnemc.com/qotw-220124

EMC Question of the Week: January 24, 2022 A device or circuit that implements the physical layer functions of the OSI model in a network interface controller is commonly called a PLT PLC PHY SerDes Answer The best answer is “c.” PHY is an abbreviation...

Question of the Week - Answer 181029https://learnemc.com/qotw-181029

EMC Question of the Week: October 29, 2018 Which of the following signal interfaces employ single-ended signaling? Ethernet (e.g. 10BASE-T) CAN and LVDS USB, DVI-D and HDMI RS-232, VGA and SCSI Answer The correct answer is "d". RS-232, VGA and SCSI are...

Question of the Week - Answer 181231https://learnemc.com/qotw-181231

EMC Question of the Week: December 31, 2018 To prevent galvanic corrosion and ensure a good electrical bond between two dissimilar metals, it is advisable to put a thin coat of varnish on both metal surfaces paint the surfaces after the connection is...

Question of the Week - Answer 240115https://learnemc.com/qotw-240115

EMC Question of the Week: January 15, 2024 To limit the radiated emissions from a transmission line that is not electrically short, the most important parameter to control is the characteristic impedance electrical balance signal amplitude common-mode...

Question of the Week - Answer 180730https://learnemc.com/qotw-180730

EMC Question of the Week: July 30, 2018 Tantalum capacitors are often favored for low-to-medium frequency circuit board decoupling because, compared to ceramic capacitors, they have a lower inductance lower ESR higher reliability higher capacitance per...

Question of the Week - Answer 220718https://learnemc.com/qotw-220718

EMC Question of the Week: July 18, 2022 In most situations, the number of vias that should be used to connect each pad of an 0402 ceramic decoupling capacitor to the power planes is 1 2 3 4 Answer The best answer is “a.” While it is important to...

Question of the Week - Answer 191007https://learnemc.com/qotw-191007

EMC Question of the Week: October 7, 2019 In order for conducted coupling to occur, the source and victim circuits must be connected at one or more points at two or more points by a wire to an LISN Answer The correct answer is "b". Conducted (or...

Question of the Week - Answer 171211https://learnemc.com/qotw-171211

EMC Question of the Week: December 11, 2017 A printed circuit board trace on an outer layer whose width is approximately equal to its distance from a solid plane on the layer below has a characteristic impedance of about, 50 Ω 70 Ω 100 Ω 150 Ω Answer...

Question of the Week - Answer 170828https://learnemc.com/qotw-170828

EMC Question of the Week: August 28, 2017 A large truck with an absolute capacitance of 1,100 pF accumulates 3 μC of charge as it travels down the road. What is the approximate voltage of the truck relative to the earth? 38 kV 13 kV 2.7 kV 1.5 kV...

Question of the Week - Answer 200113https://learnemc.com/qotw-200113

EMC Question of the Week: January 13, 2020 At the highest frequencies where a printed circuit board decoupling capacitor is still effective, its impedance is typically a negative reactance (capacitance) positive resistance positive reactance...

Question of the Week - Answer 250915https://learnemc.com/qotw-250915

EMC Question of the Week: September 15, 2025 How many fundamental EM coupling mechanisms are there? two three four more than four Answer The correct answer is “c.” The four fundamental EM coupling mechanisms are: 1. Common Impedance Coupling (aka...

Question of the Week - Answer 170724https://learnemc.com/qotw-170724

EMC Question of the Week: July 24, 2017 Which of the following transient protection components is a "crowbar" device (so called, because it acts like a short circuit when the voltage across its terminals exceeds the threshold). diode metal oxide...

Question of the Week - Answer 230904https://learnemc.com/qotw-230904

EMC Question of the Week: September 4, 2023 When evaluating the noise coupled from a microcontroller, which EM coupling mechanism is NOT likely to be significant? conducted E-field H-field radiated Answer The best answer is “d.” Noise can easily be...

Question of the Week - Answer 231120https://learnemc.com/qotw-231120

EMC Question of the Week: November 20, 2023 A circuit board trace routed over a return plane can be a significant source of radiated emissions if it is not matched is not electrically short has 90o corners none of the above Answer The best answer is...

Question of the Week - Answer 240304https://learnemc.com/qotw-240304

EMC Question of the Week: March 4, 2024 A current probe with a 10-Ω transfer impedance is connected to a 50-Ω EMI test receiver in peak detection mode. A narrow band peak is observed with an amplitude of 54 dB(μV). What is the rms value of the measured...

Question of the Week - Answer 260608https://learnemc.com/qotw-260608

EMC Question of the Week: June 8, 2026 Small unconnected copper dots or diamonds on the outer layers of a printed circuit board are an example of ground fill via stitching guard posts thieving Answer The best answer is “d.” Thieving is the addition of...

Question of the Week - Answer 200127https://learnemc.com/qotw-200127

EMC Question of the Week: January 27, 2020 A key advantage of moving to higher switching frequencies in switch-mode power converters is improved efficiency lower EMI smaller components all of the above Answer The best answer is "c". For a given supply...

Question of the Week - Answer 170327https://learnemc.com/qotw-170327

EMC Question of the Week: March 27, 2017 Of the following choices, the best material to use to shield a 60 Hz magnetic field is, copper steel lead either "b" or "c" Answer The correct answer is "b". None of these materials has a high enough...

Question of the Week - Answer 220808https://learnemc.com/qotw-220808

EMC Question of the Week: August 8, 2022 To ensure compliance with EMC requirements, most low-speed digital I/O traces longer than a few centimeters that connect to a high-speed microcontroller should have series resistors controlled impedances matched...

Question of the Week - Answer 180507https://learnemc.com/qotw-180507

EMC Question of the Week: May 7, 2018 What noise source are Electrical Fast Transient (EFT) tests designed to simulate? electrostatic discharge lightning nuclear electromagnetic pulse switched inductive loads Answer The correct answer is "d." When the...

Question of the Week - Answer 190916https://learnemc.com/qotw-190916

EMC Question of the Week: September 16, 2019 On an oscilloscope or spectrum analyzer display, dBm is an abbreviated way of representing the unit, dB(meters) dB(mV) dB(μV) dB(mW) Answer The correct answer is "d". dBm is a unit expressing decibels...

Question of the Week - Answer 220711https://learnemc.com/qotw-220711

EMC Question of the Week: July 11, 2022 Which of the following is often employed in sources of intentional electromagnetic interference (IEMI)? Marx generator Van de Graaff generator Tesla coil Flux capacitor Answer The best answer is “a.” A Marx...

Question of the Week - Answer 180305https://learnemc.com/qotw-180305

EMC Question of the Week: March 5, 2018 Twisting the wires in a wire pair carrying differential-mode signals, reduces differential-mode EM coupling to the circuit reduces common-mode EM coupling to the circuit increases the characteristic impedance all...

Question of the Week - Answer 210301https://learnemc.com/qotw-210301

EMC Question of the Week: March 1, 2021 Which 50-Ω coaxial connector type would never be secured using a torque wrench? BNC TNC N-Type SMA Answer The best answer is “a.” BNC connectors are secured with a quarter-turn of the coupling nut on the outer...

Question of the Week - Answer 190527https://learnemc.com/qotw-190527

EMC Question of the Week: May 27, 2019 X7R multi-layer ceramic capacitors are often used to provide high-frequency decoupling on printed circuit boards because, their value is independent of applied voltage their value is independent of temperature...

Question of the Week - Answer 190506https://learnemc.com/qotw-190506

EMC Question of the Week: May 6, 2019 If a 50-Ω coaxial cable has an attenuation due to conductor loss of 12 dB/km at 1 MHz, the attenuation due to conductor loss at 10 MHz is likely to be about 12 dB/km 15 dB/km 22 dB/km 38 dB/km Answer The best...

Question of the Week - Answer 180205https://learnemc.com/qotw-180205

EMC Question of the Week: February 5, 2018 Photo credit: Fischer Custom Communications A Line Impedance Stabilization Network (LISN) is necessary when measuring, conducted emissions radiated emissions electrostatic discharge immunity all of the above...

Question of the Week - Answer 230529https://learnemc.com/qotw-230529

EMC Question of the Week: May 29, 2023 To reduce the crosstalk between signals on microstrip lines, guard traces should be shorted at both ends matched at both ends floated at one end avoided Answer The best answer is “d.” Guard traces routed between...

Question of the Week - Answer 191014https://learnemc.com/qotw-191014

EMC Question of the Week: October 14, 2019 The risetime of a single EFT transient is on the order of picoseconds nanoseconds microseconds milliseconds Answer The correct answer is "b". EFT is an acronym for Electrical Fast Transient. EFT tests simulate...

Question of the Week - Answer 170910https://learnemc.com/qotw-170910

EMC Question of the Week: September 10, 2017 The skin depth in copper at 100 MHz is, about 7 microns about 7 millimeters about 70 centimeters about 7 kilometers Answer The correct answer is "a". Skin depth can be calculated using the equation δ = 1 π f...

Question of the Week - Answer 200224https://learnemc.com/qotw-200224

EMC Question of the Week: February 24, 2020 An important advantage of pseudo-differential signaling compared to differential signaling is that it doesn't require a ground conductor twisted wire pair balun DC bias voltage Answer The correct answer is...

Question of the Week - Answer 210322https://learnemc.com/qotw-210322

EMC Question of the Week: March 22, 2021 What property of a two-conductor transmission line is strongly correlated to the radiated emissions from that transmission line? characteristic impedance electrical balance differential-mode voltage common-mode...

Question of the Week - Answer 180723https://learnemc.com/qotw-180723

EMC Question of the Week: July 23, 2018 Gauss’ Law for magnetic flux, ∇∙B = 0, basically tells us that lines of magnetic flux have no beginning or end start and stop on electric charge are stronger in permeable materials are stronger in liquids Answer...

Question of the Week - Answer 200120https://learnemc.com/qotw-200120

EMC Question of the Week: January 20, 2020 In which application is active noise cancellation often a cost-effective alternative to shielding? low-frequency magnetic field interference low-frequency electric field interference interference from...

Question of the Week - Answer 210607https://learnemc.com/qotw-210607

EMC Question of the Week: June 7, 2021 The first (lowest) resonant frequency of a 40-cm x 16-cm x 38-cm rectangular metal enclosure is below 10 MHz approximately 380 MHz approximately 540 MHz above 1 GHz Answer The best answer is “c.” The resonance...

Question of the Week - Answer 200203https://learnemc.com/qotw-200203

EMC Question of the Week: February 3, 2020 Which shielding material is unlikely to be a good choice for helping to meet a conducted emissions specification? aluminum copper mumetal all of the above Answer The best answer is "c". Mumetals are...

Question of the Week - Answer 180312https://learnemc.com/qotw-180312

EMC Question of the Week: March 12, 2018 If two narrow band signals (one at 30.01 MHz and one at 30.08 MHz) both have an rms amplitude of 1.0 mV, what peak amplitude will be displayed on a 50-Ω spectrum analyzer with a 120 kHz resolution bandwidth? 1.0...

Question of the Week - Answer 211115https://learnemc.com/qotw-211115

EMC Question of the Week: November 15, 2021 Electrolytic capacitors have a relatively large capacitance for a given package size compared to ceramic capacitors making them well-suited for use as, X-capacitors in AC power filters Y-capacitors in AC...

QOTW2https://learnemc.com/qotw2

EMC Question of the Week 2021 - 2024 Available Now! This book compiles every EMC Question of the Week published on the LearnEMC website from January 2021 through December 2024. There are 212 multiple-choice questions with the correct answer and a brief...

Question of the Week - Answer 191230https://learnemc.com/qotw-191230

EMC Question of the Week: December 30, 2019 In decibels, it's the insertion gain of an amplifier that raises the signal voltage by a factor of 10. When repeated, it's very good eyesight or a year of promise and opportunity. What is 10? What is 20? What...

Question of the Week - Answer 200106https://learnemc.com/qotw-200106

EMC Question of the Week: January 6, 2020 Thyristors are generally ineffective for protecting against ESD transients, because they have too much capacitance can't handle the energy must be manually reset are too slow to turn on Answer The correct...

Question of the Week - Answer 180219https://learnemc.com/qotw-180219

EMC Question of the Week: February 19, 2018 Which of the following cables should NOT be used to convey a high-frequency differential signal? ribbon cable shielded twisted wire pair unshielded twisted wire pair coaxial cable Answer The correct answer is...

Question of the Week - Answer 190715https://learnemc.com/qotw-190715

EMC Question of the Week: July 15, 2019 Strong sources of electric-field coupling are circuits that have rapidly changing voltages rapidly changing currents large capacitors uninsulated wires Answer The best answer is "a". Electric fields are...

Question of the Week - Answer 190930https://learnemc.com/qotw-190930

EMC Question of the Week: September 30, 2019 A Hall-effect sensor exhibits a voltage at its output when exposed to an electric field a magnetic field a mechanical stress infrared light Answer The correct answer is "b". The Hall Effect describes the...