LearnEMC

LearnEMC helps companies build the in-house expertise they need to ensure their products will meet electromagnetic compatibility requirements.

[LearnEMC @LearnEmc]

EMC Question of the Week: What determines the location of the nulls in the (sin x)/x shape in the plot below?
a.) transition time
b.) duty cycle
c.) fundamental frequency

Full question and answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: A sine wave has a peak amplitude of 2.0 volts on a 50-Ω scope. The same signal on a 50-Ω spectrum analyzer would be a narrow-band peak with an amplitude of
a.) 6 dB(μV)
b.) 120 dB(μV)
c.) 123 dB(μV)
d.) 126 dB(μV)
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: One advantage of routing signals on microstrip trace pairs as opposed to stripline trace pairs is that microstrip trace pairs generally
a.) radiate less
b.) take up less space
c.) have better balance
d.) have lower loss
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: Differential trace pairs on the outer layer of a printed circuit board 0.25 mm over a solid copper plane should generally
a.) be tightly coupled
b.) be length matched
c.) have coplanar ground
d.) all of the above
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: If a digital signal trace extends a distance that exceeds its "critical length," it's generally necessary to
a.) slow the transition time
b.) provide a matched termination
c.) either (a.) or (b.)
d.) none of the above
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: A 100-Ω transfer impedance expressed in dB(Ω) is
A.) 10 dB(Ω)
B.) 20 dB(Ω)
C.) 40 dB(Ω)
D.) meaningless
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: A common-mode choke with bifilar windings generally has
a.) lower inter-winding capacitance
b.) lower leakage inductance
c.) lower resistance
d.) all of the above
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: A wireless ESD wrist strap dissipates accumulated charge using
a.) ionization
b.) radiation
c.) thermal induction
d.) none of the above
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: What is the best way to connect a decoupling capacitor to a high-speed IC on a board with power and ground planes?
Full Question and Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: What is the primary source of the ringing on the power inverter low-to-high transition shown in the figure?
a) load capacitance
b) load inductance
c) mismatched load
d) reverse-recovery current
Full question and answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: What is the mutual capacitance between a basketball and a tennis ball? Full question and answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: When a wire-pair transmission line passes through a metal plate, it's best to model the plate as a
a) plane-wave reflector
b) lumped inductance
c) lumped capacitance
d) frequency-selective surface
Full question and answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: A shielded cable connects to a circuit board mounted in a plastic enclosure. The cable shield should generally connect to the circuit board
a) directly
b) through an RC filter
c)through a CM choke
d) through ferrites
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: What is the difference between differential-mode propagation and odd-mode propagation?
a) differential-mode is undefined
b) odd-mode is undefined
c) a factor of 2
d) there is no difference

Full question and answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: If the current drawn from a DC-to-DC converter increases from 1 A to 2 A, the differential-mode conducted emissions will increase by approximately
a) 3 dB
b) 6 dB
c) between 0 and 6 dB
d) possibly less than 0 dB
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: In a conducted emissions test, moving the DUT closer to the vertical metal plane (from 40 cm to 20 cm), the value of the parasitic capacitance would increase by approximately
a) 0 dB
b) 3 dB
c) 6 dB
d) -6 dB
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: In order to filter the common-mode power bus noise effectively, which of the components shown in the figure need to be eliminated?
a) L2
b) L3
c) CY1 and CY2
d) CY3 and CY4
Full question and answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: 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?
a) 0 Ω
b) 50 Ω
c) 100 Ω
d) depends on the cable length

Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: The TDR waveform shown in the figure indicates a discontinuity 1.5 meters down the line. The discontinuity appears to be a
a) short circuit
b) open circuit
c) series inductance
d) series capacitance

Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: In order for electric-field shields to be effective, they must be
a) conductive
b) grounded
c) a skin depth or more thick
d) all of the above
Answer at https://t.co/T47iXeZnbN.