Net Electric Field: Find Magnitude Midway Between 2 Particles

[nothingatall]

Homework Statement

Two particles are fixed to an x axis: particle 1 of charge -1.23 x 10-7 C is at the origin and particle 2 of charge +1.23 x 10-7 C is at x = 15.5 cm. Midway between the particles, what is the magnitude of the net electric field?

Homework Equations

E=kQ/r^2 and/ or E=2kQ/r^2

The Attempt at a Solution

I used the first equation and I got 3.68e5 N/C then I used the second equation because there are two charges and I got 3.93e5 N/C. Both of these answers were marked wrong and I don't know why. Any help? Thanks.

 

[minimark1234]

well your halfway there if you did the math right on both of those. a major concepts of electrodynamics is the rule of superposition, which states that the electric fields at any point is the sum of all the electric fields due to each electric charge effecting your system.

 

[kerimek]

As a scientist, it is important to always double check your calculations and equations to ensure accuracy. In this case, it seems like you may have made a simple mistake in your calculations. When using the first equation, the distance, r, should be the distance from the charge at the origin (particle 1) to the point midway between the two particles. This distance is not 15.5 cm, but rather half of 15.5 cm, which is 7.75 cm. Using this distance in the equation should give you the correct answer of 2.63e5 N/C.

Similarly, in the second equation, the distance should also be half of 15.5 cm, resulting in the same answer of 2.63e5 N/C.

It is also important to note that the electric field at a point midway between two charges is the same as the electric field at the midpoint between the two charges, which is also the same as the electric field at the center of a line connecting the two charges. This means that you could have also used the equation E=2kQ/(15.5/2)^2, which would also give you the correct answer.

Overall, it is important to carefully review your work and make sure you are using the correct equations and values to get the right answer.