Shock effect ailment explanation please

i have read so much on shock and i dont understand it, i need somebody to help me with these questions
1. what is the default time shock is active on enemies?
2. how do i check how long shock last?
3. how much lightning damage do i need to do to reach the 50% cap?
4. when it says increased shock effect what is it increasing?

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3. how much lightning damage do i need to do to reach the 50% cap?

There is a formula for shock so that the damage is depends on the life of the monster.....(forget what is ailment threshold which is more advanced topic)

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K4RR0T wrote:

1. what is the default time shock is active on enemies?

2 seconds.

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2. how do i check how long shock last?

Press C and click the icon of the skill you're trying to check, make sure you're on the "Offence" tab, and look at your "Shock Duration modifier." For example, clicking the Storm Brand icon on my screen says Shock Duration modifier is +61%, which means that if no other modifiers are applied, then my Shock will last 2 * 1.61 = 3.22 seconds.

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3. how much lightning damage do i need to do to reach the 50% cap?

With no other modifiers, 100% of the enemy's Ailment Threshold, which for smaller enemies is just their maximum Life, but for endgame bosses like The Shaper, is manually set at a lower amount (estimated by players to be 25% of their maximum Life).

The formula given by the developers is: 1/2*[Damage % of Ailment Threshold]^0.4

You can reach the 50% cap by dealing less than 100% of the enemy's Ailment Threshold (maximum Life) using increased shock effect (see the answer to your question 4).

For sources of Shock that do not deal damage in Hits or are otherwise stated to be guaranteed: If you have "Advanced Mod Descriptions" enabled in Options -> UI, you should be able to "hold Alt" (technically, the "Highlight items and objects" key, in case you have rebound Alt to something else like I have) when viewing a source of Shock, such as from the Summon Skitterbots skill gem, it will describe the base Shock effect of the flat Shock in grey text underneath the source of the Shock.

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4. when it says increased shock effect what is it increasing?

The magnitude of the increased damage taken. For example, using the default formulas, if you deal 10.12% of the enemy's maximum Life as Lightning damage, your Shock will cause the enemy to take 20% increased damage. If you have 50% increased shock effect, the enemy will instead take 30% increased damage.

SOURCE:
https://pathofexile.fandom.com/wiki/Shock#Mechanics -- corroborated by Patch 3.9.0 Patch Notes at https://www.pathofexile.com/forum/view-thread/2687400

For any other knowledgeable players, please let me know if I've missed an update since patch 3.9.0 that further changed the Shock formulas.

When does it pay off to invest into shock?
I remember Enkis using shock in 3.5 or 3.6 or so, but since then never again.

I always thought this would be a great go-to mechanic to boost the dmg but at this point, i am lost telling wether it is more worth it to invest into shock rather than into crit chance/multi.

Also, is the maximum shock effect you need still at 243%?