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 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 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...

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 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 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 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 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 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 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 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...

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 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 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 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 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 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...