# EK Physics page 126 error about capacitors?

#### Tokspor

##### Full Member
Is there an error in the EK Physics book on page 126? It says that for capacitors, U = (1/2)QV. ???

#### G1SG2

##### Full Member
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is there an error in the ek physics book on page 126? It says that for capacitors, u = (1/2)qv. ???

No error. U=1/2CV^2=1/2Q^2/C=1/2QV

#### matth87

##### Full Member
Is there an error in the EK Physics book on page 126? It says that for capacitors, U = (1/2)QV. ???

U is potential energy.

I remember that formula as

PE = 1/2QV

#### Tokspor

##### Full Member
On page 118, it says the potential energy for a charge in an electric field is U = qEd. And we know that V = Ed. So shouldn't U = qV?

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#### amine2086

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On page 118, it says the potential energy for a charge in an electric field is U = qEd. And we know that V = Ed. So shouldn't U = qV?

I think you are getting confused between q and Q. q refers to just a point charge and the potential energy equation on page 118 applies to point charges only. On the other hand, Q is total charge on either plate of the parallel plate capacitor.

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