Electric force
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Topic Notes
In this lesson, we will learn:
∣Fe∣: magnitude of electric force, in newtons (N)
k: Coulomb's law constant, 9.00×109N⋅m2/C2
∣Q1∣,∣Q2∣: magnitude of each charge, in coulombs (C)
r: distance between charges, in meters (m)
- Coulomb's law, which gives the electric force that one charged object exerts on another
- Calculating electric force for different arrangements of charges
- Electrostatics deals with electric charges that are at rest ("static")
- Charge is a scalar quantity. It can be positive or negative. The positive or negative character of a charge is called polarity.
- Like gravity, electric forces act at a distance. Unlike gravity, which always pulls objects together, electric forces can either push apart or pull together charges.
- Like charges (both positive or both negative) will repel each other
- Opposite charges (one positive and one negative) will attract each other.
- Coulomb's law describes electric force (Fe).
- k (Coulomb's constant) is an experimentally determined constant that relates the size of the charges (Q1 and Q2) and radius (r¸ distance between charges) to the magnitude Fe.
- Coulomb's law only gives the magnitude of Fe and not the direction, indicated by the absolute value sign on |Fe|. Notice that k, Q, and r2 are all scalars: there are no vectors on that side of the equation that could give Fe a direction. The direction of Fe must be found by considering if the charges involved would be attracted or repelled, based on their polarities.
Coulomb's Law (Electric Force)
∣Fe∣=kr2∣Q1Q2∣∣Fe∣: magnitude of electric force, in newtons (N)
k: Coulomb's law constant, 9.00×109N⋅m2/C2
∣Q1∣,∣Q2∣: magnitude of each charge, in coulombs (C)
r: distance between charges, in meters (m)
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