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...

Question of the Week - Answer 250721https://learnemc.com/qotw-250721

EMC Question of the Week: July 21, 2025 Two-terminal surface-mount components have a length, width and height. The length is always the longest dimension longest dimension that is not the height distance between inner edges of end caps distance between...

Question of the Week - Answer 180129https://learnemc.com/qotw-180129

EMC Question of the Week: January 29, 2018 At standard temperature and pressure, air breaks down becoming an electrical conductor at field strengths of approximately 10,000 volts 30,000 volts/cm 3 MW/m2 300 MW/m2 Answer The correct answer is "b". The...

Question of the Week - Answer 180514https://learnemc.com/qotw-180514

EMC Question of the Week: May 14, 2018 Lightning rods on buildings must be electrically connected through a low-gauge wire to the primary lightning protection of all cables entering the building all metal plumbing in the building the earth all of the...

Question of the Week - Answer 200622https://learnemc.com/qotw-200622

EMC Question of the Week: June 22, 2020 Wireless charging devices, widely used for consumer devices such as phones, convey power from the transmitter to the receiver through electric fields magnetic fields radiated electromagnetic fields electron beams...

Question of the Week - Answer 230605https://learnemc.com/qotw-230605

EMC Question of the Week: June 5, 2023 The circuit board component labeled R20 in the photo is a 0.20 Ω resistor 2.0 Ω resistor 20 Ω resistor 2.0 μH inductor Answer The correct answer is “a.” The standard 3-digit code for marking SMD resistors puts an...

Question of the Week - Answer 170619https://learnemc.com/qotw-170619

EMC Question of the Week: June 19, 2017 At frequencies above 1 MHz, gapping the current-return plane in a printed circuit board is an effective way to reduce, electric-field coupling magnetic-field coupling common-impedance coupling all of the above...

Question of the Week - Answer 170410https://learnemc.com/qotw-170410

EMC Question of the Week: April 10, 2017 Air breaks down forming an arc at field strengths of approximately, 25,000 volts 250,000 volts 30,000 volts/cm 300,000 volts/cm Answer The correct answer is "c". At high temperatures or in the presence of strong...

Question of the Week - Answer 200629https://learnemc.com/qotw-200629

EMC Question of the Week: June 29, 2020 Which of the following represents a proper layout for a pi-filter on a printed circuit board? Answer The correct answer is "d". The first three options all have inputs and outputs that share a ground connection....

Question of the Week - Answer 200928https://learnemc.com/qotw-200928

EMC Question of the Week: September 28, 2020 Which of the two-port networks indicated in the figure are linear? (A) only (A) and (B) only all of them none of them Answer The correct answer is "a". Networks consisting of ideal linear passive components...

Question of the Week - Answer 210614https://learnemc.com/qotw-210614

EMC Question of the Week: June 14, 2021 The length of a resonant half-wave dipole is slightly less than a half-wavelength exactly one half-wavelength slightly more than a half-wavelength independent of the wavelength Answer The best answer is “a.” The...

Question of the Week - Answer 210913https://learnemc.com/qotw-210913

EMC Question of the Week: September 13, 2021 The x-component of an electric field at a given point is Ex = 4 V/m. The y-component of the field at that point is Ey = 3 V/m. There is no z-component. What is the magnitude of the electric field at that...

Question of the Week - Answer 251006https://learnemc.com/qotw-251006

EMC Question of the Week: October 6, 2025 Which of the IV curves shown in the figure describes the behavior of a metal oxide varistor (MOV)? Answer The best answer is “b.” Metal oxide varistors are bipolar voltage-limiting devices. The curve labeled...