Question of the Week - Answer 210927https://learnemc.com/qotw-210927

EMC Question of the Week: September 27, 2021 The common-mode rejection ratio of an ideal differential receiver is 0 0 dB 6 dB infinite Answer The correct answer is “d.” The gain a differential amplifier is the ratio of its output voltage to its...

Question of the Week - Answer 200420https://learnemc.com/qotw-200420

EMC Question of the Week: April 20, 2020 At what frequencies do currents on a circuit board take the path(s) of least resistance? DC only kHz frequencies and lower MHz frequencies and higher all frequencies Answer The best answer is "b". Currents tend...

Question of the Week - Answer 231211https://learnemc.com/qotw-231211

EMC Question of the Week: December 11, 2023 The input to a 1-MHz inverting buck-boost converter is +5 V and the output is -3.3 V. Which of the board layouts shown here is least likely to exhibit unacceptable conducted or radiated emissions if layer 2...

Question of the Week - Answer 260302https://learnemc.com/qotw-260302

EMC Question of the Week: March 2, 2026 For a differential signal propagating on a balanced pair of microstrip traces, what is the difference between differential-mode propagation and odd-mode propagation? differential-mode is undefined odd-mode is...

Question of the Week - Answer 230102https://learnemc.com/qotw-230102

EMC Question of the Week: January 2, 2023 Ideally, for EMC and signal integrity, digital signals should have matched terminations when the propagation delay is large compared to the transition time the bit width 1 nanosecond 1 picosecond (i.e., always)...

Question of the Week - Answer 250421https://learnemc.com/qotw-250421

EMC Question of the Week: April 21, 2025 The voltage standing wave ratio (VSWR) in a transmission line is a function of the line's characteristic impedance and the source impedance termination impedance both (a) and (b) neither (a) nor (b) Answer The...

Question of the Week - Answer 241021https://learnemc.com/qotw-241021

EMC Question of the Week: October 21, 2024 Peaks in the radiated emissions from an electronic device are well above the CISPR 32 limit at 350, 370, and 390 MHz. They are found to be due to a 10-MHz signal from a clock driver that is distributed to two...

Question of the Week - Answer 251013https://learnemc.com/qotw-251013

EMC Question of the Week: October 13, 2025 The conduction currents in a transmission line flow in the conductors in the dielectric towards the load in small eddies Answer The best answer is “a.” By definition, conduction currents are the result of...

Question of the Week - Answer 200217https://learnemc.com/qotw-200217

EMC Question of the Week: February 17, 2020 The far-field radiated emissions from a vertically polarized 30-MHz source located one-meter above a ground plane have a maximum value at the ground plane 1 meter above the ground plane between 1 and 4 meters...

Question of the Week - Answer 200601https://learnemc.com/qotw-200601

EMC Question of the Week: June 1, 2020 For the DC/DC buck converter shown in the figure, the switching voltage node is the trace and pads connecting the converter IC to Cin Cout L GND Answer The correct answer is "c". The switching voltage node (i.e....

Question of the Week - Answer 220620https://learnemc.com/qotw-220620

EMC Question of the Week: June 20, 2022 The often-cited contact discharge waveform in IEC 61000-4-2 (shown here) plots the voltage in kV vs. time in μs voltage in kV vs. time in ns current in kA vs. time in μs current in A vs. time in ns Answer The...

Question of the Week - Answer 190401https://learnemc.com/qotw-190401

EMC Question of the Day: April 1, 2019 Which of the following was the earliest EMC innovation? lightning rod copper tape ground strap ferrite beads Answer The correct answer is "a." Cave paintings made more than 10,000 years ago depict tall man-made...

Question of the Week - Answer 220613https://learnemc.com/qotw-220613

EMC Question of the Week: June 13, 2022 In a balanced transmission line, both signal conductors have the same voltage current cross-section impedance to ground Answer The correct answer is “d.” By definition, both conductors in an electrically balanced...

Question of the Week - Answer 211025https://learnemc.com/qotw-211025

EMC Question of the Week: October 25, 2021 A 250-Mbps clock driver transmits a signal on a 50-Ω coaxial cable to the 50-Ω input of a 1-GHz digital oscilloscope. The sampling rate of the oscilloscope is 5 GSa/sec. If the actual transition time of the...

Question of the Week - Answer 240408https://learnemc.com/qotw-240408

EMC Question of the Week: April 8, 2024 A 1-Gbps clock driver transmits a signal on a 50-Ω coaxial cable to the 50-Ω input of a 4-GHz digital oscilloscope. The sampling rate of the oscilloscope is 20 GSa/sec. If the actual transition time of the signal...

Question of the Week - Answer 240212https://learnemc.com/qotw-240212

EMC Question of the Week: February 12, 2024 A 15-kV potential difference causes the air between two points to break down forming a 1-cm arc. The arc extinguishes when the voltage drops below the threshold current drops below the threshold temperature...

Question of the Week - Answer 220822https://learnemc.com/qotw-220822

EMC Question of the Week: August 22, 2022 The substitution method and closed-loop method describe two types of ESD tests conducted emissions tests electrical fast transient tests bulk current injection tests Answer The correct answer is “d.” Bulk...

Question of the Week - Answer 231127https://learnemc.com/qotw-231127

EMC Question of the Week: November 27, 2023 A pair of parallel wires separated by a distance, s, carries 1 mA of differential mode current, IDM. The same pair of wires carries 1 mA of common-mode current, ICM, at the same frequency. If the wire...

Question of the Week - Answer 251215https://learnemc.com/qotw-251215

EMC Question of the Week: December 15, 2025 Circuits operating at voltages greater than 50 volts and circuits whose conductors may come into contact with humans must generally have isolated safety grounds EMC grounds current returns all of the above...

Question of the Week - Answer 250908https://learnemc.com/qotw-250908

EMC Question of the Week: September 8, 2025 Two devices in an EMI test setup contribute to radiated emissions at 85 MHz. One produces a radiated field strength of 40 dB(μV/m) at the measurement location. The other produces a radiated field strength of...

Question of the Week - Answer 210329https://learnemc.com/qotw-210329

EMC Question of the Week: March 29, 2021 At high frequencies, the magnitude of the magnetic field tangential to a metal surface, such as the copper plane in a circuit board, is approximately equal to zero the surface current density on the plane the...

Question of the Week - Answer 210531https://learnemc.com/qotw-210531

EMC Question of the Week: May 31, 2021 The far-end crosstalk (FEXT) between two single-ended signals routed on parallel stripline traces with matched terminations is generally much less than the near-end crosstalk much greater than the near-end...

Question of the Week - Answer 210906https://learnemc.com/qotw-210906

EMC Question of the Week: September 6, 2021 The hand-held probe shown in the figure (an electrically small loop) measures voltage current electric fields magnetic fields Answer The best answer is “d.” The voltage produced by the probe is the result of...

Question of the Week - Answer 240520https://learnemc.com/qotw-240520

EMC Question of the Week: May 20, 2024 For estimating the common-mode current, a ferrite core clamped around a cable is best modeled as a common-mode resistance common-mode inductance common-mode choke capacitance to infinity Answer The best answer is...

Question of the Week - Answer 250407https://learnemc.com/qotw-250407

EMC Question of the Week: April 7, 2025 A circuit board mounted on a metal chassis communicates with another circuit board mounted on a different metal chassis several meters away. The 100-Mbps differential communication signal is conveyed over a...

Question of the Week - Answer 211206https://learnemc.com/qotw-211206

EMC Question of the Week: December 6, 2021 The EM test environment depicted in this image is an anechoic chamber a semi-anechoic chamber a TEM cell a GTEM cell Answer The correct answer is “d.” We can rule out the first two options, because the floor...

Question of the Week - Answer 200810https://learnemc.com/qotw-200810

EMC Question of the Week: August 10, 2020 A TDR is connected to the input of a 50-Ω cable and measures the waveform indicated on the right. The cable is terminated with a 150-Ω resistor and a parasitic series inductance shunt inductance series...

Question of the Week - Answer 211018https://learnemc.com/qotw-211018

EMC Question of the Week: October 18, 2021 A 3-Mbps clock signal is transmitted to a 5-pF load on a 15-cm microstrip trace. The trace capacitance is 10 pF. The clock source resistance is 2 Ω. Which component should be placed in series with the clock...

Question of the Week - Answer 250616https://learnemc.com/qotw-250616

EMC Question of the Week: June 16, 2025 Many cables with foil shields have an extra uninsulated wire called a drain wire. The main purpose of the drain wire is to provide mechanical strength a path for low-frequency current an earth ground connection a...

Question of the Week - Answer 200427https://learnemc.com/qotw-200427

EMC Question of the Week: April 27, 2020 When high-speed pseudo-differential signals are transmitted between circuit boards on an unshielded ribbon cable, a key concern is the differential-mode radiation from the cable common-mode voltage driving the...

Question of the Week - Answer 210823https://learnemc.com/qotw-210823

EMC Question of the Week: August 23, 2021 For the purposes of high-frequency EM modeling, a round wire can generally be modeled as a flat strip and flat strips can generally be modeled as round wires. To do this, how should the width of the strip, w,...

Question of the Week - Answer 241216https://learnemc.com/qotw-241216

EMC Question of the Week: December 16, 2024 An 8-layer circuit board has solid half-ounce copper planes on Layers 2, 3, 5 and 7. At 10 kHz, magnetic field lines passing through the circuit board induce eddy currents primarily in which layer(s)? Layer 2...

Question of the Week - Answer 250317https://learnemc.com/qotw-250317

EMC Question of the Week: March 17, 2025 In products that meet all of their EMC requirements, the circuit boards are typically isolated from chassis ground shielded circular green Answer The best answer is “d.” Of course, the color of the circuit board...

Question of the Week - Answer 230123https://learnemc.com/qotw-230123

EMC Question of the Week: January 23, 2023 Which power circuit topology is generally used when it is necessary to isolate the input current-return from the output current-return? Buck Boost H-Bridge Flyback Answer The best answer is “d.” Of the four...

Question of the Week - Answer 210510https://learnemc.com/qotw-210510

EMC Question of the Week: May 10, 2021 Two circuits send signals down a 300-meter cable and share the same return conductor. Circuit 1 delivers 120-volt, 60-Hz power to a 100-ohm load. 170 mV of coupled 60-Hz noise appears at the load end of Circuit 2...

Question of the Week - Answer 250310https://learnemc.com/qotw-250310

EMC Question of the Week: March 10, 2025 One way to reduce the thermal noise floor of an EMI test receiver measurement by 20 dB is to reduce the room temperature from 20 oC to 2 oC. reference level from 20 dBm to 0 dBm resolution bandwidth from 100 kHz...

Question of the Week - Answer 251020https://learnemc.com/qotw-251020

EMC Question of the Week: October 20, 2025 The displacement current in a transmission line flows back and forth in a direction that is ____________ relative to the direction of the wave propagation. parallel perpendicular circular at a 45° angle Answer...

Question of the Week - Answer 200615https://learnemc.com/qotw-200615

EMC Question of the Week: June 15, 2020 The best component to use to protect the RESET input of a microcontroller from indirect ESD events is usually a resistor capacitor varistor ferrite bead Answer The best answer is "a". Field coupling from an ESD...

Question of the Week - Answer 230925https://learnemc.com/qotw-230925

EMC Question of the Week: September 25, 2023 The best low-pass filter option for a high-impedance (capacitive) input is usually a series inductor series resistor shunt capacitor series ferrite Answer The best answer is “b.” While all of the options...

Question of the Week - Answer 250210https://learnemc.com/qotw-250210

EMC Question of the Week: February 10, 2025 One advantage of a 50-μH LISN compared to a 5-μH LISN is that the 50-μH LISN can make measurements at higher frequencies at lower frequencies on AC powerlines on DC powerlines Answer The best answer is “b.”...

Question of the Week - Answer 250825https://learnemc.com/qotw-250825

EMC Question of the Week: August 25, 2025 Which material property is primarily responsible for the loss in a high-frequency ferrite bead or ferrite core used for EMI suppression? complex permittivity complex permeability conductivity eddy currents...

Question of the Week - Answer 250414https://learnemc.com/qotw-250414

EMC Question of the Week: April 14, 2025 The main EMC-related advantage of twisting a pair of parallel wires is that it reduces the far-field radiation near-field coupling inductance per unit length all of the above Answer The best answer is “b.” A...

Question of the Week - Answer 240909https://learnemc.com/qotw-240909

EMC Question of the Week: September 9, 2024 During an immunity test, the field strength measured inside a test chamber is 160 dB(μV/m). After the test equipment is powered down, the measured field strength due to the EUT is 40 dB(μV/m). So, powering...

Question of the Week - Answer 210222https://learnemc.com/qotw-210222

EMC Question of the Week: February 22, 2021 The three phase wires connecting a high-voltage power inverter to a remote AC motor should be unshielded be individually shielded have one shield covering all three wires both b and c. Answer The best answer...

Question of the Week - Answer 240826https://learnemc.com/qotw-240826

EMC Question of the Week: August 26, 2024 A DC/DC converter (9V-to-12V, 600 kHz, 15 W) originally failed to meet conducted and radiated emissions requirements. The design was revised to include pi-filters and common-mode chokes on the power input and...

Question of the Week - Answer 240930https://learnemc.com/qotw-240930

EMC Question of the Week: September 30, 2024 An active device is mounted on an 8-layer board with a GND plane on Layer 4 and a VCC plane on Layer 5. Which of the four decoupling capacitors depicted in the figure provides the best high-frequency...

Question of the Week - Answer 200914https://learnemc.com/qotw-200914

EMC Question of the Week: September 14, 2020 The SI-derived unit for magnetic field intensity is gauss tesla weber/m2 ampere/m Answer The best answer is "d". The first three choices are all units of magnetic flux density. In the SI system, magnetic...

Question of the Week - Answer 200511https://learnemc.com/qotw-200511

EMC Question of the Week: May 11, 2020 A coaxial cable has a 2-cm inner conductor diameter and a 7-cm outer conductor diameter. If the dielectric between the conductors is air, what is the ratio of the E-field magnitude to H-field magnitude for a TEM...

Question of the Week - Answer 200831https://learnemc.com/qotw-200831

EMC Question of the Week: August 31, 2020 In a multiwire transmission line, parallel signal conductors carry currents I1 and I2, respectively, where I1 and I2 point in the same direction. The common-mode current on the wire pair is I1 - I2 I1 + I2 (I1...

Question of the Week - Answer 211213https://learnemc.com/qotw-211213

EMC Question of the Week: December 13, 2021 Electrical products and systems with floating grounds are generally unsafe unlikely to meet radiated emissions requirements all of the above none of the above Answer The best answer is “d.” The term "floating...