Electrostatic Force Questions

[SyrianHero]

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In the Physics Kaplan book, there is a question that states: What direction does a negative electrostatic force point? What direction does a positive electrostatic force point? The answer for the negative electrostatic force is: "It points from one charge to the other (attractive)", but I'm not sure how they got this without knowing what charge the force is acting on. Can anyone explain this?

 

[aalamruad]

In the Physics Kaplan book, there is a question that states: What direction does a negative electrostatic force point? What direction does a positive electrostatic force point? The answer for the negative electrostatic force is: "It points from one charge to the other (attractive)", but I'm not sure how they got this without knowing what charge the force is acting on. Can anyone explain this?

Part of calculating electrostatic force is finding the product of the two charges in question (take a look at Coulomb's law). Thus, the product of a positive charge and a negative charge gives a negative value, while the product of two like charges (+ and + or - and -) will give a positive value. So oppositely charged particles will have a negative electrostatic force, and we all know that oppositely charged particles move towards each other (attractive force), while similarly charged particles will experience a repulsive force.

Unlike charges: (negative charge)(positive charge) = negative electrostatic force = attraction

Like charges: (positive charge)(positive charge) or (negative charge)(negative charge) = positive electrostatic force = repulsion

I think you may have confused "negative electrostatic force" with "negative charge."

 

[aldol16]

In the Physics Kaplan book, there is a question that states: What direction does a negative electrostatic force point? What direction does a positive electrostatic force point? The answer for the negative electrostatic force is: "It points from one charge to the other (attractive)", but I'm not sure how they got this without knowing what charge the force is acting on. Can anyone explain this?

It doesn't matter what charge the force is acting on. If you know it's an attractive force, it should be obvious that the force vector will point from one charge to the other (Newton's Third says that if the force vector from one charge points towards the other charge, then the force vector from the other charge will point towards the first charge with the same magnitude). In other words, the electrostatic force will cause acceleration of the charges towards one another, regardless of what each charge is (given that they are oppositely-charged, which is necessary to have a negative force to begin with).

So imagine this. Charge 1 is positively charged and charge 2 is negatively charged. You know that the force is negative (attractive). How would you draw the vector for the force acting on charge 1? Charge 2? Now repeat the thought experiment and reverse the charges.