# physics

Consider three charges q1 = 6.0 µC, q2 = 1.8 µC, and q3 = -2.8 µC, arranged as shown below.
Q1 is positive and is 3 cm away from Q2. Q2 is also positive and is 2 cm away from Q3 which is negative.
(a) What is the electric field at a point 1.0 cm to the left of the middle charge?
(b) What is the magnitude of the force on a 1.1 µC charge placed at this point?

1. 👍 0
2. 👎 0
3. 👁 675
1. Electric field at a distance r from a charge q is given by Coulomb's law:
E = k q / r^2

To get the E-field, you have to add the contribution of 3 charges:

E1 = k q1 / r1^2
E2 = k q2 / r2^2
E3 = k q3 / r3^2

You can look at the geometry and so simple addition and subtraction to get the three r's. They give you the three q's. Don't worry about sign just yet. Let all the numbers above be positive.

Then you add them up, but you have to be a little careful nowabout direction. Let's call right positive. q1 is to the left of the point and positive. Positive charges push the E-field away, so it's to the right, and positive. q2 is to the right of the point and positive, so it pushes left (negative). q3 is to the right and negative, so it pulls right (positive).

So Etotal = E1 - E2 + E3 (positive answer means to the right)

And of cource, the force of that E-field on a test charge q, is just:
F = qE

1. 👍 0
2. 👎 0

## Similar Questions

1. ### physic

two point charges are placed on the x axis as follows: charge q1 = +4.00 nc is located at x = 0.200 m, and charge q2 = +5.00 nc is at x = -0.300 m what ae the magnitude and direction of the net force exerted by these two charges

2. ### Physics

Two electrostatic point charges of +60.0 uC and +50.c uC exert a repulsive force on each other of 175 N. What is the distance between the two charges?

3. ### Physics

Two equal charges are separated by 3.7 x 10^-10 m. The force between the charges has a magnitude of 2.37 x 10^-3 N. What is the magnitude of q on the charges? can some one explain to me how to do this step by step. Not that great

4. ### physics

Which of the following statements about electric field lines due to static charges are true? (Select all that apply.) Electric field lines can never cross each other. Static charges can create closed loop electric field lines that

1. ### Science

Two identical point charges repel each other with a force of 4N. When the charges are moved 5mm further apart, the resultant force is reduced to 1N. How far apart were the charges originally?

2. ### Physics

How would the electrostatic force change if Coulomb's law included a negative sign? It would depend on the magnitude of the charges. Like charges would attract, and opposite charges would repel.*** It would not make a difference

3. ### Physics

Two particles having charges of +0.500nC and +8.00nC are separated by a distance of 1.20m. (a) at what point along the line connecting the two charges is the net electric field due to the two charges equal to zero? (b) where would

4. ### MEC

two charges repel each other with a force of 0.1N when they are 5cm apart. Find the forces between the same charges when they are 2cm and 8cm apart.

1. ### Science

Two point charges are 10.0 cm apart and have charges of 2.0 μC and –2.0 μC, respectively. What is the magnitude of the electric field at the midpoint between the two charges? 8.99*10^9(2*10^-6/.025)=719200 Two equal charges

2. ### physics

Two charges, -17 and +3.6 µC, are fixed in place and separated by 3.2 m. a) At what spot along a line through the charges is the net electric field zero? Locate this spot relative to the positive charge. (Hint: The spot does not

3. ### Physics

Two point charges are 10.0 cm apart and have charges of 2.0 μC and –2.0 μC, respectively. What is the magnitude of the electric field at the midpoint between the two charges? 8.99*10^9(2*10^-6/.025)=719200 Two equal charges

4. ### physics

Two charges, -37 µC and +3 µC, are fixed in place and separated by 2.8 m. (a) At what spot along a line through the charges is the net electric field zero? Locate this spot relative to the positive charge. (Hint: The spot does