maths/physics questionn help pls Watch

h26
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So at around 3:36 of this vid and onwards I am a bit confused https://www.youtube.com/watch?v=ks1B1_umFk8

So the formula is confusing me the most .. so how do you know what value for the charge you put in ?
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Gregorius
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(Original post by h26)
So at around 3:36 of this vid and onwards I am a bit confused https://www.youtube.com/watch?v=ks1B1_umFk8

So the formula is confusing me the most .. so how do you know what value for the charge you put in ?
The setup they're using in the video is that a fixed charge Q produces an electric field E (measured in Joules per Coulomb). You then introduce a charge into the electric field of Q' coulombs; the potential energy of the Q' charge will then be EQ'.

Usually in these situations you use a large charge Q and a small charge Q', so that the field produced by Q' doesn't mess things up. However, in the video, they introduce a charge Q' of 2 Coulombs, which is gigantic!
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h26
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(Original post by Gregorius)
The setup they're using in the video is that a fixed charge Q produces an electric field E (measured in Joules per Coulomb). You then introduce a charge into the electric field of Q' coulombs; the potential energy of the Q' charge will then be EQ'.

Usually in these situations you use a large charge Q and a small charge Q', so that the field produced by Q' doesn't mess things up. However, in the video, they introduce a charge Q' of 2 Coulombs, which is gigantic!
Thanks but in the end they still subbed in the smaller charge into the formula at 6:42 so not sure
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Gregorius
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(Original post by h26)
Thanks but in the end they still subbed in the smaller charge into the formula at 6:42 so not sure
Yes, that's right; they're take Q as the charge that produces the electric field, and Q' as the charge that is affected by that electric field.
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(Original post by Gregorius)
The setup they're using in the video is that a fixed charge Q produces an electric field E (measured in Joules per Coulomb). You then introduce a charge into the electric field of Q' coulombs; the potential energy of the Q' charge will then be EQ'.

Usually in these situations you use a large charge Q and a small charge Q', so that the field produced by Q' doesn't mess things up. However, in the video, they introduce a charge Q' of 2 Coulombs, which is gigantic!
Ah I get that now thanks a lot!
Just a quick question:
Ypu said "You then introduce a charge into the electric field of Q' coulombs; the potential energy of the Q' charge will then be EQ'."

would the potential energy of the Q charge also be EQ' so like the same as that of Q'?

"that's right; they're take Q as the charge that produces the electric field, and Q' as the charge that is affected by that electric field"
Wouldn't the Q' also produce an electric field so Q can be affected by the electric field of Q'?
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