Relationship: Force on a charge at some distance from capacitor Plates

In summary, when comparing the forces |F1| and |F2| felt by charges placed at d/2 and d/4 on two capacitor plates with uniform charge distribution but different charges, the forces are equal due to the constant and uniform electric field between the plates.
  • #1
Minhtran1092
28
2

Homework Statement



Two capacitor plates (infinite plane) with uniform charge distribution but different charges (one positive, one negative) are distance "d" apart. A charge is place at d/2 and feels force |F1|. A charge is placed at d/4 and feels force |F2|. How does |F1| compare to |F2|?

Homework Equations



F=qE (Force on a test charge is proportional to the electric field at the point charge)
E = η/ε0 (η = Q/A, charge distribution); Electrical field between two parallel plate capacitors

The Attempt at a Solution



The electrical field between two parallel plate capacitors is constant and uniform in direction at any point. Since F=qE, E is constant and 'q' is negligible, F≈E everywhere. Thus, |F1|=|F2|.
 
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  • #2
That looks good except for the statement F≈E. q is assumed negligible in the sense that it is assumed q does not disturb the uniform charge distributions on the plates. But that doesn't mean that you can ignore q in the equation F = qE. Do you see that your answer is still valid even for F = qE?
 
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Related to Relationship: Force on a charge at some distance from capacitor Plates

1. What is the relationship between force and distance from capacitor plates?

The force on a charge at some distance from capacitor plates is inversely proportional to the square of the distance. This is known as the inverse square law, meaning that as the distance increases, the force decreases.

2. How does the charge on the capacitor plates affect the force on a charge outside the plates?

The force on a charge at some distance from capacitor plates is directly proportional to the charge on the plates. This means that as the charge on the plates increases, the force on a charge outside the plates also increases.

3. What is the direction of the force on a charge outside capacitor plates?

The direction of the force on a charge outside capacitor plates depends on the charge of the plates and the charge of the external charge. Like charges will repel each other, while opposite charges will attract each other.

4. How does the area of the capacitor plates affect the force on a charge outside the plates?

The force on a charge at some distance from capacitor plates is directly proportional to the area of the plates. This means that as the area of the plates increases, the force on a charge outside the plates also increases.

5. Can the force on a charge outside capacitor plates be negative?

Yes, the force on a charge at some distance from capacitor plates can be negative. This means that the force is in the opposite direction of the force caused by the electric field of the plates. This can occur when the external charge is of the opposite sign as the charge on the plates.

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