Question of the Week - Answer 190603https://learnemc.com/qotw-190603

EMC Question of the Week: June 3, 2019 Which of the following N-port network parameters is equal to the voltage reflection coefficient at one of the ports? S11 S12 Z11 Z12 Answer The correct answer is "a". S-parameters relate the voltage waves...

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 191118https://learnemc.com/qotw-191118

EMC Question of the Week: November 18, 2019 A ferrite bead should be placed in series with the ground connection on analog-to-digital converters on stable voltage references when the app note specifies it all of the above none of the above Answer The...

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 260119https://learnemc.com/qotw-260119

EMC Question of the Week: January 19, 2026 In order for electric-field shields to be effective, they must be conductive grounded a skin depth or more thick all of the above Answer The best answer is “a.” Electric field shields work by allowing charge...

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...

Question of the Week - Answer 170710https://learnemc.com/qotw-170710

EMC Question of the Week: July 10, 2017 Common-Impedance coupling is likely to be the dominant coupling mechanism when the source circuit is operating at, low frequencies and low impedances low frequencies and high impedances high frequencies and low...

Question of the Week - Answer 190819https://learnemc.com/qotw-190819

EMC Question of the Week: August 19, 2019 Generally, if an indirect ESD test toggles the reset input on a microcontroller, the reset input trace needs to be rerouted a TVS diode a capacitor a series resistor Answer The best answer is "d". Indirect ESD...

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 181217https://learnemc.com/qotw-181217

EMC Question of the Week: December 17, 2018 Which of the following cable transfer impedance measurements corresponds to the cable with the best shielding? 1 mΩ 10 MΩ 0 dB 100 dB Answer The correct answer is "a". Cable transfer impedance measurements...

Question of the Week - Answer 191209https://learnemc.com/qotw-191209

EMC Question of the Week: December 9, 2019 At a discontinuity in a transmission line, the ratio of incident power to reflected power in decibels is generally referred to as the reflection coefficient transmission coefficient insertion loss return loss...

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 180226https://learnemc.com/qotw-180226

EMC Question of the Week: February 26, 2018 On circuit boards that have a layer devoted to "ground" it is very important to, minimize the number of via holes in this layer minimize the diameter of all via holes provide isolated ground areas for each...

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...

Question of the Week - Answer 241230https://learnemc.com/qotw-241230

EMC Question of the Week: December 30, 2024 A 20-cm LCD display assembly is connected to a printed circuit board through a 15-cm cable. The cable carries 8 single-ended, 100-Mbps video data signals plus several low-frequency control signals. A good...

Question of the Week - Answer 211129https://learnemc.com/qotw-211129

EMC Question of the Week: November 29, 2021 In a multi-layer printed circuit board, a via that connects a trace on an outer layer to traces on one or more inner layers, but does not pass all the way through the board, is called a blind via buried via...

Question of the Week - Answer 200720https://learnemc.com/qotw-200720

EMC Question of the Week: July 20, 2020 A spectrum analyzer with a 9 kHz resolution bandwidth detects a narrow band signal at 1.01 MHz with an amplitude of 40 dB(μV) and another narrowband signal at 1.03 MHz with an amplitude of 35 dB(μV). What peak...

Question of the Week - Answer 230206https://learnemc.com/qotw-230206

EMC Question of the Week: February 6, 2023 The symbol in the figure indicates the presence of ESD sensitive components an ESD ground lightning protection dangerous voltages Answer The best answer is “d.” This symbol is defined in ISO 7010 (W012) and...

Question of the Week - Answer 241014https://learnemc.com/qotw-241014

EMC Question of the Week: October 14, 2024 Which of these three V-I curves corresponds to the transient voltage suppression (TVS) diode schematically represented in the figure? (a) (b) (c) (b) or (c) Answer The best answer is “a.” The unipolar TVS...

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 its 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 210412https://learnemc.com/qotw-210412

EMC Question of the Week: April 12, 2021 The TDR waveform in the figure indicates a discontinuity in a 50-Ω transmission line. Which of the following most closely models the discontinuity? 8 μH series inductor 80 pH shunt inductor 8 μF series capacitor...

Question of the Week - Answer 230327https://learnemc.com/qotw-230327

EMC Question of the Week: March 27, 2023 The 1-MHz buck converter layout in this figure is poorly done. Layer 2 is a solid GND plane. Cin connects to GND. Cout connects to PGND. Every ground pin of the converter IC connects to both PGND and GND. Which...

Question of the Week - Answer 210118https://learnemc.com/qotw-210118

EMC Question of the Week: January 18, 2021 In the figure on the right representing a cross-sectional view of a 3.3-V trace over a ground plane, the lines encircling the trace represent electric field lines magnetic field lines equipotential lines...

Question of the Week - Answer 230911https://learnemc.com/qotw-230911

EMC Question of the Week: September 11, 2023 The most important feature of TVS diodes used for transient protection on a DC power input is that they are bidirectional have low capacitance have low connection inductance have three terminals Answer The...

Question of the Week - Answer 210503https://learnemc.com/qotw-210503

EMC Question of the Week: May 3, 2021 Generally, Class 2 multilayer ceramic capacitors (e.g. X7R) should not be used in filter designs where there is no DC bias because they are polarized they are active devices their ESR is too high their capacitance...

Question of the Week - Answer 240101https://learnemc.com/qotw-240101

EMC Question of the Week: January 1, 2024 When a circuit board with a ground plane is mounted to a metal supporting structure, the ground plane and the supporting structure should almost always be connected directly through capacitors with a large...

Question of the Week - Answer 210426https://learnemc.com/qotw-210426

EMC Question of the Week: April 26, 2021 When the terminal voltage exceeds a pre-defined maximum level, voltage-limiting transient protection devices hold the voltage to that maximum. On the other hand, "crowbar" devices act like a switch and pull the...

Question of the Week - Answer 220404https://learnemc.com/qotw-220404

EMC Question of the Week: April 4, 2022 Ground fault circuit interrupters (GFCIs) interrupt the connection to the power source when they detect a significant current flowing on the ground conductor significant difference in the currents flowing on the...

Question of the Week - Answer 170626https://learnemc.com/qotw-170626

EMC Question of the Week: June 26, 2017 60 Hz electric field shielding is best accomplished using materials that have a, high conductivity high permeability high permittivity high atomic weight Answer The correct answer is "a". Materials with a high...

Question of the Week - Answer 211220https://learnemc.com/qotw-211220

EMC Question of the Week: December 20, 2021 A biconical antenna transmits 100 Watts of power at 200 MHz in a semi-anechoic environment. What is the maximum field strength 3 meters from the antenna? 300 V/m 30 V/m 3 V/m 30 dB(μV/m) Answer The best...

Question of the Week - Answer 221003https://learnemc.com/qotw-221003

EMC Question of the Week: October 3, 2022 A narrow-band radiated emissions failure at 1.56 GHz is correlated to the operation of a CAN-FD transceiver communicating at 8 Mbps. Which of the following is the most likely source of this emission? cable...

Question of the Week - Answer 180709https://learnemc.com/qotw-180709

EMC Question of the Week: July 9, 2018 Which of the following devices is used to connect a balanced antenna to a coaxial cable? impedance matching circuit high-pass filter low-pass filter balun Answer The correct answer is "d." A balun is a device that...

Question of the Week - Answer 210920https://learnemc.com/qotw-210920

EMC Question of the Week: September 20, 2021 What is the maximum power that could be radiated from a 50-MHz source with a source impedance of 2 Ω and an open-circuit rms voltage of 1.5 volts? < 1 nW 56 mW 280 mW > 1 Watt Answer The best answer is “c.”...

Question of the Week - Answer 190826https://learnemc.com/qotw-190826

EMC Question of the Week: August 26, 2019 A signal flowing on a 2-conductor transmission line generates common-mode noise when it encounters an inductance in the return conductor a change in the characteristic impedance a change in the electrical...

Question of the Week - Answer 191202https://learnemc.com/qotw-191202

EMC Question of the Week: December 2, 2019 At the third harmonic, the quasi-peak value of the radiated emissions from a 25-MHz clock (square wave) source is equal to the peak value 3 dB lower than the peak value 6 dB lower than the peak value 6 dB...

Question of the Week - Answer 181203https://learnemc.com/qotw-181203

EMC Question of the Week: December 3, 2018 What effect does increasing the resolution bandwidth of a spectrum analyzer from 9 kHz to 120 kHz generally have on the noise floor? no significant effect increases it by 11 dB increases it by 22 dB decreases...

Question of the Week - Answer 181224https://learnemc.com/qotw-181224

EMC Question of the Week: December 24, 2018 Approximately, what is the maximum voltage coupled to a circuit with a 1.4 m2 loop area from a 60-Hz magnetic field that has a peak amplitude of 15 A/m? 1 mV 10 mV 100 mV 1 V Answer Using Faraday’s Law, the...

Question of the Week - Answer 190304https://learnemc.com/qotw-190304

EMC Question of the Week: March 4, 2019 A printed circuit board trace on an external layer with a width approximately equal to its height above a current-return plane has a characteristic impedance of approximately, 10 Ω 50 Ω 75 Ω 100 Ω Answer The...

Question of the Week - Answer 190610https://learnemc.com/qotw-190610

EMC Question of the Week: June 10, 2019 According to Ampere’s Law, electric currents are always surrounded by electric fields magnetic fields magnetic currents conductors Answer The correct answer is "b". The integral form of Ampere’s Law is: ∮ H → ⋅ d...