Question

I know the answer to this Electrostatics question, but how do I get there? Here is the question with the answer:

"A + 4.75 microC and a -3.55 microC charge are placed 18.5 cm apart. Where can a third charge be placed so that it experiences no net force?"

Answer: .116 m (if my source is accurate)

@abhisar Someone recommended me to you, can you help me??

Answer 1

Give me a sec.

Answer 2

Ok, sorry I was helping someone else...

Answer 3

So, for this question I'll give you few examples on how to solve similar problems.

Answer 4

These are called equilibrium questions and we are trying to find the Null Point which is a point where the net force is zero.

Answer 5

There are two cases

Case 1 When both the charges given are similar i.e either both are positive or both are negative.

In this case we use the following formula,

\(\sf \huge \boxed{ x = \frac{\sqrt{q_1}}{\sqrt{q_1}+\sqrt{q_2}}}\times r\)

Answer 6

Example: Two charges are 4C and 9C kept at 30 m from each other. Find a place where third charge should kept so that it receives 0 net force.


Solution: Here. \(\sf q_1\) will be the smaller charge and \(\sf q_2\) will be the bigger charge. r is the distance between the two charge.


Plugging in the values we get,

\(\sf \huge \frac{2}{2+3}\times 30\) = 12 m. Now this means we should keep the third charge 12 m away from the 4C charge in the direction of 4C charge.

Answer 7

Similarly, In case II when the given charges are unlike you use the following formula.

\(\boxed{ \sf \huge x = \frac{\sqrt{q_1}}{\sqrt{q_1}-\sqrt{q_2}}\times r}\)

Answer 8

Your original question is similar to CaseII.

Answer 9

Okay, actually I think I figured it out (was not sure at first). Thank you very much :)!

Answer 10

Example, Two charges 9C and -4C are placed 10 m apart. Find where should a third charge be placed so that it experiences a 0 net force.


Solution:

\(\huge \mathcal{ \frac{2}{2-3}\times 10=-20}\)

This means the third charge should be kept at a distance of 20m from the charge 4C in direction of 4C charge.

Answer 11

Okay, actually I think I figured it out (was not sure at first). Thank you very much :)!