Question of the Week - Answer 220912https://learnemc.com/qotw-220912

EMC Question of the Week: September 12, 2022 To reduce electric-field coupling to an electrically short cable, the cable shield must be grounded on at least one end grounded on both ends floated on both ends rigid and continuously grounded Answer The...

Question of the Week - Answer 231204https://learnemc.com/qotw-231204

EMC Question of the Week: December 4, 2023 Which of the following components in parallel with a ceramic capacitor is most likely to be responsible for narrowband emissions above 1 GHz? resistor tantalum capacitor ceramic capacitor (same value) ceramic...

Question of the Week - Answer 220829https://learnemc.com/qotw-220829

EMC Question of the Week: August 29, 2022 A power bus decoupling capacitor that meets the high-frequency current needs of one pin of one component is generally referred to as a _________ decoupling capacitor. local high-frequency single-point X Answer...

Question of the Week - Answer 251117https://learnemc.com/qotw-251117

EMC Question of the Week: November 17, 2025 Changing the transition times of a 1-MHz trapezoidal waveform from 2 ns to 50 ns causes the harmonics above what frequency to start falling off at 40 dB/decade instead of 20 dB/decade? 1 MHz 7 MHz 70 MHz 80...

Question of the Week - Answer 231218https://learnemc.com/qotw-231218

EMC Question of the Week: December 18, 2023 In order to be galvanically isolated, two circuits cannot share a DC current path any current path any wires or components a ground Answer The best answer is “a.” Galvanic isolation requirements prevent the...

Question of the Week - Answer 250707https://learnemc.com/qotw-250707

EMC Question of the Week: July 7, 2025 If a board-mounted common-mode choke connects directly to the connector pins, with no Y-capacitors in between, then the common-mode choke should be bifilar wound low loss lossy removed Answer The best answer is...

Question of the Week - Answer 230703https://learnemc.com/qotw-230703

EMC Question of the Week: July 3, 2023 Which of the following is a name commonly used to describe hardware or software that monitors a system and implements a reset when problems are detected? watchdog squirrel cage mother hen eagle scout Answer The...

Question of the Week - Answer 250120https://learnemc.com/qotw-250120

EMC Question of the Week: January 20, 2025 Which of the following antennas is generally the most practical for making radiated emissions measurements in a semi-anechoic environment between 10 and 100 MHz? resonant dipole biconical log-periodic dipole...

Question of the Week - Answer 210809https://learnemc.com/qotw-210809

EMC Question of the Week: August 9, 2021 In well-designed systems, conductors labeled "ground" never carry differential signal currents single-ended signal currents power currents noise currents Answer The best answer is “a.” Of course, giving an...

Question of the Week - Answer 200309https://learnemc.com/qotw-200309

EMC Question of the Week: March 9, 2020 When designing a power line filter, the decision to put an inductor on one line as opposed to both lines depends primarily on whether one side is grounded the cost of each option the maximum current the required...

Question of the Week - Answer 220905https://learnemc.com/qotw-220905

EMC Question of the Week: September 5, 2022 The white cylindrical power-input component on the left of this figure has "F.T.6.3A" engraved on its endcap. This component is almost certainly a gas discharge tube metal oxide varistor axial capacitor fuse...

Question of the Week - Answer 200504https://learnemc.com/qotw-200504

EMC Question of the Week: May 4, 2020 An important parameter for estimating the RF immunity of a differential signaling system is the receiver's CMRR BFF RFIL RFQL Answer The best answer is "a". The Common-Mode Rejection Ratio (CMRR) is a measure of...

Question of the Week - Answer 211011https://learnemc.com/qotw-211011

EMC Question of the Week: October 11, 2021 A person wearing leather shoes shuffles across a polyester carpet on a dry day collecting a significant charge. The polarity of the charge is positive is negative depends on the season depends on the...

Question of the Week - Answer 200302https://learnemc.com/qotw-200302

EMC Question of the Week: March 2, 2020 Electrically small loop antennas are widely used to detect and measure electric fields magnetic fields far-field radiation conducted emissions Answer The correct answer is "b". Electrically small loops produce a...

Question of the Week - Answer 200907https://learnemc.com/qotw-200907

EMC Question of the Week: September 7, 2020 In order to prevent differential-mode to common-mode conversion, what property of an electrical connector needs to be matched to the signal conductors on both ends? wave velocity characteristic impedance...

Question of the Week - Answer 250811https://learnemc.com/qotw-250811

EMC Question of the Week: August 11, 2025 Which of the following is NOT one of Maxwell's equations? Ohm's Law Gauss's Law Ampere's Law Faraday's Law Answer The best answer is “a.” Ohm's law is an equation from circuit theory. It's field-theory...

Question of the Week - Answer 201123https://learnemc.com/qotw-201123

EMC Question of the Week: November 23, 2020 Which of the following EMC test standards does NOT describe a procedure for measuring radiated emissions? ANSI C63.4 CISPR 32 IEC 61000-4-2 MIL-STD-461G Answer The best answer is "c". IEC 61000-4-2 is a...

Question of the Week - Answer 220801https://learnemc.com/qotw-220801

EMC Question of the Week: August 1, 2022 For optimum performance in radiated emissions testing, the circuit ground in high-speed printed circuit boards should normally be well-connected to the chassis ground connected to chassis ground at a single...

Question of the Week - Answer 200406https://learnemc.com/qotw-200406

EMC Question of the Week: April 6, 2020 According to IEC 60417, which of the following is NOT a ground symbol? Answer The correct answer is "c". This inverted triangle symbol is commonly used to represent a local circuit reference on a printed circuit...

Question of the Week - Answer 240812https://learnemc.com/qotw-240812

EMC Question of the Week: August 12, 2024 Three of the four electromagnetic coupling mechanisms are proportional to the source current. Which one is proportional to the source voltage? conducted coupling electric-field coupling magnetic-field coupling...

Question of the Week - Answer 241028https://learnemc.com/qotw-241028

EMC Question of the Week: October 28, 2024 Which 2-port S-parameter value is consistent with a vector network analyzer measurement of a lossless cable that connects Port 1 to Port 2? |S­11| = 0 dB |S­11| = 3 dB |S­21| = 0 dB |S­12| = -∞ dB Answer The...

Question of the Week - Answer 210719https://learnemc.com/qotw-210719

EMC Question of the Week: July 19, 2021 In 12-V (or 42-V) automotive components, the circuit board's "ground" planes should normally be tied to any existing nearby chassis ground through capacitors capacitors in parallel with a resistance capacitors in...

Question of the Week - Answer 211101https://learnemc.com/qotw-211101

EMC Question of the Week: November 1, 2021 A dot on an inductor package indicates the location of the input current terminal external winding terminal shield connection terminal core Answer The best answer is “b.” When inductors have several layers of...

Question of the Week - Answer 210125https://learnemc.com/qotw-210125

EMC Question of the Week: January 25, 2021 A 1-kΩ resistor in series with a CMOS input pin on a microcontroller can help to improve conducted emissions radiated emissions ESD immunity all of the above Answer The best answer is “d.” Internal noise...

Question of the Week - Answer 220502https://learnemc.com/qotw-220502

EMC Question of the Week: May 2, 2022 A digital signal source drives a 20-cm microstrip trace terminated with a CMOS input at 10 Mbps. The sum of the trace capacitance and the input capacitance is 18 pF. Which component below would be a good choice to...

Question of the Week - Answer 240701https://learnemc.com/qotw-240701

EMC Question of the Week: July 1, 2024 Most TEM cells used for EM emissions and immunity testing have a characteristic impedance equal to 50 Ω 75 Ω 100 Ω 377 Ω Answer The best answer is “a". Most TEM cells have a 50-Ω characteristic impedance in order...

Question of the Week - Answer 250303https://learnemc.com/qotw-250303

EMC Question of the Week: March 3, 2025 Two RLCG lumped parameter models for a twisted wire pair transmission line are shown in the figure. One of them uses one R and one L value to model the resistance and inductance per unit length. The other uses...

Question of the Week - Answer 210621https://learnemc.com/qotw-210621

EMC Question of the Week: June 21, 2021 You're in an aluminum canoe in the middle of a large lake when a thunderstorm approaches. To protect yourself from lightning, you should row towards shore swim towards shore turn the canoe over and get under it...

Question of the Week - Answer 241104https://learnemc.com/qotw-241104

EMC Question of the Week: November 4, 2024 At data rates from 1 Mbps to 100 Mbps most of the signal attenuation/dispersion in long microstrip traces and long unshielded twisted wire pairs (e.g., CAT5e) is typically due to conductor loss dielectric loss...

Question of the Week - Answer 220509https://learnemc.com/qotw-220509

EMC Question of the Week: May 9, 2022 For a given magnetic field strength, the voltage detected by a magnetic-field probe (electrically small loop or coil) connected to a 50-Ω spectrum analyzer is independent of frequency proportional to frequency (a)...

Question of the Week - Answer 240603https://learnemc.com/qotw-240603

EMC Question of the Week: June 3, 2024 The walls of a particular shielding enclosure have a nominal thickness of 60 mils. This is equal to 0.06 inches 0.17 inches 6 mm 6 cm Answer The correct answer is “a.” One mil is equal to 0.001 inches. This may be...

Question of the Week - Answer 240916https://learnemc.com/qotw-240916

EMC Question of the Week: September 16, 2024 The yellow components on the circuit board in the figure are in series with some of the low-speed I/O traces. These components are probably resistors capacitors inductors TVS diodes Answer The best answer is...

Question of the Week - Answer 220425https://learnemc.com/qotw-220425

EMC Question of the Week: April 25, 2022 Generally, to meet radiated emissions requirements, circuit board traces carrying digital signals faster than 1 Mbps should NOT make 90-degree turns cross over gaps in the ground plane have unmatched...

Question of the Week - Answer 220214https://learnemc.com/qotw-220214

EMC Question of the Week: February 14, 2022 Nearly all electronic keyboards are protected from electrostatic discharge by TVS diodes ESD rings a plastic membrane antistatic keys Answer The correct answer is “c.” Keyboards typically have a plastic...

Question of the Week - Answer 221010https://learnemc.com/qotw-221010

EMC Question of the Week: October 10, 2022 If a resistor network is labeled 101, the value of each resistor in the network is likely to be 1 Ω 10 Ω 100 Ω 101 Ω Answer The correct answer is “c.” When the code used to label a resistor consists of 3...

Question of the Week - Answer 230424https://learnemc.com/qotw-230424

EMC Question of the Week: April 24, 2023 When connecting a solder pad or a connector pin to a solid plane in a circuit board, it is not unusual to make the connection using four spokes as illustrated in the figure. This is called a thermal relief...

Question of the Week - Answer 240819https://learnemc.com/qotw-240819

EMC Question of the Week: August 19, 2024 A particular source delivers 2.0 mW of power to a 50-Ω receiver when they are directly connected. When they are connected through 20 cm of 50-Ω coaxial cable, the received power is only 1.8 mW due to cable...

Question of the Week - Answer 241111https://learnemc.com/qotw-241111

EMC Question of the Week: November 11, 2024 When is the decoupling capacitor, trace, and via placement indicated in this figure appropriate? almost always when the VDD and GND planes are closely spaced when the VDD and GND planes are widely spaced...

Question of the Week - Answer 250519https://learnemc.com/qotw-250519

EMC Question of the Week: May 19, 2025 The primary purpose of printed circuit board shields is to reduce conducted coupling radiated coupling near-field coupling power bus noise Answer The best answer is “c.” Shielding the circuits/components on a...

Question of the Week - Answer 220418https://learnemc.com/qotw-220418

EMC Question of the Week: April 18, 2022 In terms of shielding effectiveness, the most important dimension of a slot or seam in a shielding enclosure is generally its length thickness depth area Answer The best answer is “a.” Length is by far the most...

Question of the Week - Answer 211122https://learnemc.com/qotw-211122

EMC Question of the Week: November 22, 2021 If a plane wave propagating in a 50-Ω TEM cell has an electric field strength of 100 V/m, the magnetic field strength is approximately 0 A/m 0.27 A/m 2.0 A/m 3.77 A/m Answer The correct answer is “b.” The...

Question of the Week - Answer 230130https://learnemc.com/qotw-230130

EMC Question of the Week: January 30, 2023 At 100 MHz, the plane-wave shielding effectiveness of a pane of glass (5 mm thick, εr = 8) is approximately 0 dB -3 dB 3 dB 6 dB Answer The best answer is “a.” A pane of glass that is thin relative to a...

QOTWhttps://learnemc.com/qotw

EMC Question of the Week 2017 - 2020 On March 13, 2017, LearnEMC began posting an EMC Question of the Week on their website at LearnEMC.com. Each week a new multiple-choice question is posted along with a link to the correct answer and a brief...

Question of the Week - Answer 201221https://learnemc.com/qotw-201221

EMC Question of the Week: December 21, 2020 On a circuit board where R1 is a resistor, C1 is a capacitor, and L1 is an inductor, B1 is most likely a ferrite bead varistor diode decoupling capacitor Answer The correct answer is "d". The B indicates a...

Question of the Week - Answer 250602https://learnemc.com/qotw-250602

EMC Question of the Week: June 2, 2025 A certain microstrip trace pair has a differential-mode impedance equal to 100 Ω and a common-mode impedance equal to 40 Ω. Determine termination impedances Z1, Z2 and Z12 required to match both the common-mode...

Question of the Week - Answer 250922https://learnemc.com/qotw-250922

EMC Question of the Week: September 22, 2025 At 100 MHz, a tinted window (σ = 10-12 S/m, εr = 8, thickness = 3 mm) has a plane wave shielding effectiveness of approximately 0 dB 2 dB 4 dB 6 dB Answer The best answer is “a.” The magnitude of the...

Question of the Week - Answer 220314https://learnemc.com/qotw-220314

EMC Question of the Week: March 14, 2022 Two 0.1-μF capacitors are placed in series with a high-speed differential trace pair on a circuit board to block low-frequency noise. Which of the following would generally be the best choice for these...

Question of the Day - Answer 200401https://learnemc.com/qotw-200401

EMC Question of the Day: April 1, 2020 What is the optimum number of grounds to use in a mixed-signal circuit board layout? 0 1 2 the more, the better Answer The correct answer is "d". Signal voltages and currents can cause conducted and radiated...

Question of the Week - Answer 240513https://learnemc.com/qotw-240513

EMC Question of the Week: May 13, 2024 To meet radiated emissions requirements, a product that plugs into a wall outlet should ensure that the outlet's earth ground is well-connected to the circuit board ground frame ground both of the above none of...

Question of the Week - Answer 200323https://learnemc.com/qotw-200323

EMC Question of the Week: March 23, 2020 Low-frequency analog signal returns are sometimes isolated from digital signal returns in order to prevent eddy currents electric field coupling common impedance coupling single-point grounds Answer The correct...