Why are common mode filters / chokes necessary?

In which locations can common mode filters (common mode chokes) be effectively used as EMC countermeasure components?

Please provide instructions on how to select common mode filters (common mode chokes).

TDK’s common mode filters (common mode chokes) include multilayer products, thin-film products, and wire wound products, but what are their differences (features)?

It seems that there is no mark indicating the winding direction (polarity) on common mode filters / chokes. If their directions are different when they are mounted, would the properties change?

Are there any problems in mounting common mode filters / chokes in GND-signal lines?

Can common mode filters / chokes be used on the primary side of a power supply? Can common mode filters / chokes be used in AC lines?

Are there any problems in mounting common mode filters / chokes for signal lines?

Where can I confirm the weight of common mode filters (common mode chokes)?

Do common mode filters / chokes generate heat?

Where can I view a list of TDK’s common mode filters (common mode chokes)?

Where can the reflow conditions of TDK’s common mode filters (common mode chokes) be confirmed?

Provide instructions on how to measure impedance of a common mode filter / choke.

What is the difference between common mode and differential mode?

What is differential insertion loss?

What is common mode attenuation?

What is Scd21?

Which voltage location is being referred to for the rated voltage of a common mode filter (common mode choke)?

Can common impedance be considered impedance that affects only AC (resonant signals)?

At which frequency is the "impedance," which is the representative characteristic of common mode filters / chokes, defined?

What is the defining condition for the rated current of common mode filters / chokes?

Is it okay to use a common mode filter / choke if a current larger than its rated current is applied momentarily?

What is the difference between common mode impedance, differential mode impedance and characteristic impedance?

Where is the characteristic impedance described?

What is the cutoff frequency?

Where can I check the frequency characteristics of the common mode impedance?

Where can I check the insertion loss?

Where can I see the RoHS certificate or REACH certificate?

In there any display on the product model no. that provides information such as whether the product is lead-free?

Can your products be disposed of as normal industrial waste?