Easy electro charge question, calculation error?

In summary, the conversation was about finding the charges of two point charges given that their sum is +11μC and they experience a force of 194 N when 2.9 cm apart. The equations used were F = KqQ/r^2 and q + Q = Net charge, and the solution involved solving a quadratic equation. However, the mistake was made with the units of the charge, which should have been microcoulombs instead of coulombs.
  • #1
Paulkaryote
1
0

Homework Statement



The sum of two point charges is + 11μC. When they are 2.9 cm apart, each experiences a force of 194 N. Find the charges given that the force is:
(a)Repulsive
(b)Attractive
(In microNewtons)

Homework Equations


F = KqQ/r^2
q + Q = Net charge

The Attempt at a Solution


I confirmed this with my friend and he got the same answer as me, so maybe we are both making the same mistake.

q + Q = 11 => q = 11 - Q
F = kq(11-Q)/r^2 => 194 = (9x10^9)(11-Q)Q/(0.029)^2
After solving and simplifying the quadratic I got Q = 11 and 1.6*10^-12 which is wrong.
 
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  • #2
Paulkaryote said:

Homework Statement



The sum of two point charges is + 11μC. When they are 2.9 cm apart, each experiences a force of 194 N. Find the charges given that the force is:
(a)Repulsive
(b)Attractive
(In microNewtons)

Homework Equations


F = KqQ/r^2
q + Q = Net charge

The Attempt at a Solution


I confirmed this with my friend and he got the same answer as me, so maybe we are both making the same mistake.

q + Q = 11 => q = 11 - Q
F = kq(11-Q)/r^2 => 194 = (9x10^9)(11-Q)Q/(0.029)^2
After solving and simplifying the quadratic I got Q = 11 and 1.6*10^-12 which is wrong.

Welcome to PF, Paulkaryote.

What happened to the units attached to the charge? They were not Coulombs, but microcoulombs.
 

FAQ: Easy electro charge question, calculation error?

What is an electro charge?

An electro charge is a fundamental property of matter that determines how it interacts with electromagnetic fields. It can be positive or negative, and is measured in units of coulombs (C).

How do I calculate electro charge?

To calculate electro charge, you need to know the amount of charge (in coulombs) and the potential difference (in volts). The electro charge is equal to the product of the charge and potential difference, so Q = CV.

What is the equation for calculating electro charge?

The equation for calculating electro charge is Q = CV, where Q is the charge in coulombs, C is the capacitance in farads, and V is the potential difference in volts.

How can I avoid calculation errors when working with electro charge?

To avoid calculation errors when working with electro charge, it is important to double check your calculations and make sure you are using the correct units. It can also be helpful to use a calculator or spreadsheet for more complex calculations.

What are some common sources of error when working with electro charge?

Some common sources of error when working with electro charge include using incorrect units, rounding errors, and errors in measurement. It is also important to make sure your equipment is calibrated properly and there are no external factors affecting your measurements.

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