Using the corrected distances, we can calculate the electric fields due to each charge at x = -2.0 cm.
For the first charge (at the origin):
E₁ = k(q₁) / r₁² = (8.99e9)(6.5e-6) / (0.02²) = 1.44875e7 N/C
For the second charge (at x = 10.0 cm):
E₂ = k(q₂) / r₂² = (8.99e9)(-1.5e-6) / (0.12²) = -8.985e5 N/C
Since both fields are in the same direction (to the left, as they repel from the positive charge and attract to the negative one), we add the magnitudes to get the net electric field:
E_net = E₁ + E₂ = 1.44875e7 - 8.985e5 = 1.35891e7 N/C
Two point charges lie on the x axis. A charge of + 6.5 µC is at the origin, and a charge of -1.5 µC is at x = 10.0 cm.
What is the net electric field at x = -2.0 cm?
I found the electrical field for each charge using the equation E= k(q)/ r^2. My calculations were:
For the first charge- (8.99e9)(6.5e-6)/(.2^2) = 1460875 and (8.99e9)(1.5e-6)/(.2 + .1)^2 = 149833.33 for the second. I added the two to determine the net field- 1610708.33N/C. This answer was incorrect. So then I used -1.5e-6, recalculated and got net of 1311041.67; also incorrect. Can anyone tell me if I am I using the wrong equation or doing something else wrong?
You are doing something else wrong. The distance from charge 1 to the point where the field is desired is 0.02 m, not 0.2. Likewise for charge 2, it is 0.1 + 0.02m , not 0.1 + 0.2.
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