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 180402https://learnemc.com/qotw-180402

EMC Question of the Week: April 2, 2018 You’re relatively safe in a car during a thunderstorm because, lightning won’t strike cars with rubber tires the car battery neutralizes any charge build-up on the car the radio antenna acts like a lightning rod...

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...

Question of the Week - Answer 191104https://learnemc.com/qotw-191104

EMC Question of the Week: November 4, 2019 At 1 MHz, the plane-wave shielding effectiveness of a 1-mm thick sheet of lead is, is close to 0 dB is approximately 20 dB is more than 100 dB could be less than 0 dB Answer The correct answer is "c". While...

Question of the Week - Answer 240722https://learnemc.com/qotw-240722

EMC Question of the Week: July 22, 2024 Radiation from electrically small loops is proportional to loop area, but when it comes to meeting EM emissions requirements, radiation from electrically small circuits is usually negligible proportional to loop...

Question of the Week - Answer 251201https://learnemc.com/qotw-251201

EMC Question of the Week: December 1, 2025 Some of the power in a signal propagating on a transmission line can be converted from differential-mode to common-mode when the signal experiences electrical imbalance a change in electrical imbalance a...

Question of the Week - Answer 210802https://learnemc.com/qotw-210802

EMC Question of the Week: August 2, 2021 On average, how does reducing the duty cycle from 50% to 25% while maintaining the same period and transition times affect the amplitude of the harmonics of a pulse train above 1/(πtr)? They increase They...

Question of the Week - Answer 250217https://learnemc.com/qotw-250217

EMC Question of the Week: February 17, 2025 By design, the twisted wire pairs in a CAT6 cable all have slightly different characteristic impedances wire diameters twist rates imbalance factors Answer The best answer is “c.” Although the twist rate is...

Question of the Week - Answer 190121https://learnemc.com/qotw-190121

EMC Question of the Week: January 21, 2019 Ferrite beads have an impedance that is best described as an inductance a capacitance a frequency-dependent resistance an open circuit Answer The best answer is "c." Ferrite beads consist of a lossy ferrous...

Question of the Week - Answer 230612https://learnemc.com/qotw-230612

EMC Question of the Week: June 12, 2023 A wrist strap like the one in the figure is often worn by people working on electronic equipment to keep them from being electrocuted damaging the equipment working too hard leaving the work area Answer The best...

Question of the Week - Answer 170821https://learnemc.com/qotw-170821

EMC Question of the Week: August 21, 2017 A current probe with a transfer impedance of 10 Ω is connected to a 50-Ω spectrum analyzer. A single narrow-band peak is observed with an amplitude of -57 dBm. What is the rms value of the measured current? 68...

Question of the Week - Answer 250714https://learnemc.com/qotw-250714

EMC Question of the Week: July 14, 2025 The sum of the currents flowing into a circuit node (e.g., a circuit board signal trace) is essentially zero as long as we can neglect the parasitic inductances parasitic capacitances parasitic resistances laws...

Question of the Week - Answer 240805https://learnemc.com/qotw-240805

EMC Question of the Week: August 5, 2024 With a shorted termination, the inductance measured at the input of a 2-meter coaxial cable is 510 nH. With an open termination, the capacitance measured at the input is 200 pF. How long does it take a signal to...

Question of the Week - Answer 170717https://learnemc.com/qotw-170717

EMC Question of the Week: July 17, 2017 The algebraic sum of all the voltages around any closed path in a circuit equals zero. true false Answer Electrical engineers will recognize the sentence above as a statement of Kirchhoff's Voltage Law (KVL)....

Question of the Week - Answer 210208https://learnemc.com/qotw-210208

EMC Question of the Week: February 8, 2021 In order to control the transition times of CMOS digital logic, it's generally best to use a series resistor series ferrite series inductor shunt capacitor Answer The best answer is “a.” The transition times...

Question of the Week - Answer 260202https://learnemc.com/qotw-260202

EMC Question of the Week: February 2, 2026 A digital clock driver transmits a signal on a 50-Ω coaxial cable to a 50-Ω load. What value of source resistance maximizes the power delivered to the load? 0 Ω 50 Ω 100 Ω depends on cable length Answer The...

Question of the Week - Answer 230501https://learnemc.com/qotw-230501

EMC Question of the Week: May 1, 2023 A signal propagates as a plane wave in a transmission line with a 125-Ω characteristic impedance. It reaches an interface with another transmission line that has the same characteristic impedance, but a different...

Question of the Week - Answer 210111https://learnemc.com/qotw-210111

EMC Question of the Week: January 11, 2021 The semi-transparent gray or pink bags that electronic products are often shipped in are excellent conductors slightly conductive excellent insulators magnetic field shields Answer The correct answer is “b.”...

Question of the Week - Answer 230417https://learnemc.com/qotw-230417

EMC Question of the Week: April 17, 2023 At MHz frequencies, which EM coupling mechanism tends to be the main contributor to crosstalk between matched parallel microstrip traces on a circuit board? common impedance electric field magnetic field both...

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 171226https://learnemc.com/qotw-171226

EMC Question of the Week: December 26, 2017 Placing a 1kΩ resistor in series with the reset input of a microprocessor, has no effect on the voltage required to reset the processor can help to prevent inadvertent resets due to coupled noise can reduce...

Question of the Week - Answer 180611https://learnemc.com/qotw-180611

EMC Question of the Week: June 11, 2018 Twisting a pair of wires, as opposed to routing them side-by-side, nearly doubles the characteristic impedance nearly halves the characteristic impedance typically increases the characteristic impedance about 5%...

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 180115https://learnemc.com/qotw-180115

EMC Question of the Week: January 15, 2018 Coupling from low-flying planes at 400 Hz disrupts a particular sensor in an automotive system affecting the navigation system. The coupling mechanism must be, common impedance coupling electric or magnetic...

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 180625https://learnemc.com/qotw-180625

EMC Question of the Week: June 25, 2018 Two circuit board traces are routed 0.25 mm over a half-ounce copper current-return plane. One trace carries a 5-volt digital signal and is terminated with a 10-pF load capacitance. The minimum transition time of...

Question of the Week - Answer 191216https://learnemc.com/qotw-191216

EMC Question of the Week: December 16, 2019 A computer keyboard malfunctions when it is placed on a desktop near a power strip. There is nothing plugged into the power strip, and the keyboard works fine when the power strip is moved further away. What...

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 180820https://learnemc.com/qotw-180820

EMC Question of the Week: August 20, 2018 Eventually, a connection between a copper wire and an aluminum screw may exhibit an increase in resistance due to galvanic corrosion a decrease in resistance due to galvanic corrosion an increased voltage due...

Question of the Week - Answer 181119https://learnemc.com/qotw-181119

EMC Question of the Week: November 19, 2018 Which of the following receiver impedances receives the most average power from a 50-Ω source? 25 Ω 25 + j25 Ω j50 Ω 50 + j50 Ω Answer The correct answer is "a". Most electrical engineers would recognize that...

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 180917https://learnemc.com/qotw-180917

EMC Question of the Week: September 17, 2018 What value of shunt capacitor should be used to make a low-pass filter with an insertion loss of 20 dB at 65 MHz in a circuit where both the source and load impedances are 50 ohms? 940 pF 979 pF 985 pF 0.001...

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 190225https://learnemc.com/qotw-190225

EMC Question of the Week: February 25, 2019 Differential-mode signals propagating down a transmission line are partially converted to common-mode noise when the transmission line, is unbalanced experiences a change in the balance experiences a change...