Electric fields created by charged particles

1. Jan 23, 2009

perfection256

1. The problem statement, all variables and given/known data

At a particular moment, three small charged balls, one negative and two positive,are located as shown in Figure 13.46. Q1 = 1 nC, Q2 = 5 nC, and Q3 = -2 nC.

Remember that you must first convert all quantities to S.I. units. 1 nC = 1 nanocoulomb = 1e-9 C.

(a1) What is the electric field at the location of Q1, due to Q2?
(a2) What is the electric field at the location of Q1, due to Q3?

(c1) What is the electric field at location A, due to Q1?
(c2) What is the electric field at location A, due to Q2?
(c3) What is the electric field at location A, due to Q3?

(d) An alpha particle (He2+, containing two protons and two neutrons) is released from rest at location A. At the instant the particle is released, what is the electric force on the alpha particle, due to Q1, Q2 and Q3?

2. Relevant equations

|E|= kq/|r^2|

3. The attempt at a solution

(a1) (9e^9)(5x10^-9)/(.0016) *<0,.04,0>= <0,1125,0>
(a2) (9e^9)(-2x10^-9)/(.0009) * <.03,0,0>=<300,0,0>

(c1) (9e^9)(1x10^-9)/(.0009)* <.03,0,0>=<300,0,0>
(c2) (9e^9)(5x 10^-9)/(.0025)* <.03,.04,0>=<540,720,0>
(c3) (9e^9)(-2x 10^-9)/(.0016)* <0,.04,0)=<0,-450,0>

2. Jan 23, 2009

__JR__

The equation you need here is $$E = \frac{kq}{r^2} * \hat{r}$$, where k is the permitivity of free space.

$$\hat{r}$$ represents the radial unit vector from the point charge to the point where you are calculating the electric field, and shouldn't have a magnitude. (I think your * < x,y,z> is indicating that you're multiplying by a magnitude, which would be incorrect).

Also, since this is a vector field, use their coordinate system and stay consistent.

Last edited: Jan 23, 2009
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