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Home Q & A Board Science-Related Homework Help Physics
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gerrard gerrard
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12 years ago
Consider the two charges Q1 = 2.0 x 10-7 C, and Q2 = -2.0 x 10-7 C, held 15 cm. from each other. Find:
1)   The magnitude of the force between the two charges. [10 marks]
2)   The magnitude and direction of the electric field at point O midway between the charges? [10 marks]
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#1
12 years ago
Coulomb's Law: F= [k(q1)(q2)]/r^2. So to find the force, just plug in (but convert cm to m first, and k, or Coulomb's constant is equal to about 8.99x10^9). Therefore, you will get F=[(8.99x10^9)(2.0 x 10^-7)(-2.0 x 10^-7)]/.15^2=-0.01598 N.
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calcguycalcguy
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12 years ago
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#3
12 years ago
Use coulomb's law for both problems.

For the first part, F = k q1 q2 / r^2. Don't forget to convert the cm.

For the second part, E = k q / r^2. So figure out the halfway distance and calculate the two E-fields. When adding the vectors up, you have to make sure to keep the directions straight. The positive charge has e-field lines pointing away from itself. The negative charge has lines pointing in. So they end up adding up in this case.
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