Electrostatics [Electric Field]

AI Thread Summary
The discussion centers on calculating the electric field at point P, which is 5.00 cm from the origin, with two charges positioned 20.0 cm from the origin. The user initially calculated the electric fields due to each charge but arrived at a net electric field of 4794.67 N/C, which contradicts the answer key's value of 19200 N/C. A key misunderstanding involves the distance used in the calculations; the user mistakenly used 25 cm for the distance from the -50 nC charge to point P instead of the correct 25 cm. Clarification is provided that the -50 nC charge is indeed 25 cm from point P, leading to the need for corrected calculations to match the answer key. Accurate distance measurements are crucial for determining the electric field correctly.
format1998
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Homework Statement



(Please see attachment)
Point P is 5.00 cm from the origin and each charge is 20.0 cm from the origin.

Q1= -50.0 nC (20.0 cm from the origin on the -x axis)
Q2= +30.0 nC (20.0 cm from the origin on the +x axis)
Point P is 5.00 cm from the origin (in the +x axis)

Homework Equations



E = kQ/r2
ENET=E1+E2


The Attempt at a Solution



E1 = (8.99E9 Nm2/C2)((-50E-9 C)/(.25m)2) = -7192 N/C

E2 = (8.99E9 Nm2/C2)((+30E-9 C)/(.15m)2)= 11986.7 N/C

ENET=ENET=E1+E2=-7192 N/C + 11986.7 N/C = 4794.67 N/C, -x

According to the answer key, the answer is 19200 N/C, -x. What am I not understanding?

Please help! Any and all help is much appreciated.
 

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format1998 said:

Homework Statement



(Please see attachment)
Point P is 5.00 cm from the origin and each charge is 20.0 cm from the origin.

Q1= -50.0 nC (20.0 cm from the origin on the -x axis)
Q2= +30.0 nC (20.0 cm from the origin on the +x axis)
Point P is 5.00 cm from the origin (in the +x axis)

Homework Equations



E = kQ/r2
ENET=E1+E2


The Attempt at a Solution



E1 = (8.99E9 Nm2/C2)((-50E-9 C)/(.25m)2) = -7192 N/C

E2 = (8.99E9 Nm2/C2)((+30E-9 C)/(.15m)2)= 11986.7 N/C

ENET=ENET=E1+E2=-7192 N/C + 11986.7 N/C = 4794.67 N/C, -x

According to the answer key, the answer is 19200 N/C, -x. What am I not understanding?

Please help! Any and all help is much appreciated.

To me it looks like the diagram has 20cm for the left charge, but your equations use 25cm. Am I misreading your diagram?
 
I need to find the magnitude of the Electric Field at point P. The charge on the left (-50 nC) is 20 cm from the origin, point P is another 5 cm to the right of the origin. So, the -50 nC charge is 25 cm from point P.
 
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