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184_notes:pc_force [2018/05/24 13:22] – [General Relationship] curdemma | 184_notes:pc_force [2021/01/26 21:26] – [General Relationship] bartonmo | ||
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Sections 3.7, 13.2 - 13.3 , and 13.6 of Matter and Interactions (4th edition) | Sections 3.7, 13.2 - 13.3 , and 13.6 of Matter and Interactions (4th edition) | ||
- | [[184_notes: | + | /*[[184_notes: |
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+ | [[184_notes: | ||
===== Electric Force ===== | ===== Electric Force ===== | ||
- | You have read about the [[184_notes: | + | Last week, you have read about the [[184_notes: |
In general, there are two ways to think about the electric force: either one charge interacts with another charge or one charge interacts with the electric field that is produced by another charge. We will usually favor thinking about how charges interact with the field (rather than how charges interact with other charges) because it is through that field that the interaction occurs. These notes will introduce the general relationship between electric force and electric field and discuss the example of a positive and negative point charges (which we will call an electric dipole). | In general, there are two ways to think about the electric force: either one charge interacts with another charge or one charge interacts with the electric field that is produced by another charge. We will usually favor thinking about how charges interact with the field (rather than how charges interact with other charges) because it is through that field that the interaction occurs. These notes will introduce the general relationship between electric force and electric field and discuss the example of a positive and negative point charges (which we will call an electric dipole). | ||
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$$\vec{F}_{net \rightarrow q}=q*\vec{E}_{net}$$ | $$\vec{F}_{net \rightarrow q}=q*\vec{E}_{net}$$ | ||
- | Where we are using the notation of $net \rightarrow q$ to show that this is the force //from// the net electric field //on// the charge q. Since electric field is a vector and charge is a scalar, when they are multiplied together, the result is a vector (electric force). This vector points in the same direction as the electric field for positive charges and in the opposite direction of the electric field in the case of negative charges. **Note that this is the electric force from the //external electric field// on the // | + | Where we are using the notation of $net \rightarrow q$ to show that this is the force //from// the net electric field //on// the charge q. Since electric field is a vector and charge is a scalar, when they are multiplied together, the result is a vector (electric force). This vector points in the same direction as the electric field for positive charges and in the opposite direction of the electric field in the case of negative charges. **Note that this is the electric force from the //external electric field// on the // |
+ | |||
+ | //Note: there is some ambiguity about the direction of the force as it would matter which kind of charge is placed in the field.// | ||
- | The electric force works in same way as any other force that you learned about in Mechanics: | + | The electric force works in the same way as any other force that you learned about in Mechanics: |
- | * The electric force has units of newtons (N). | + | |
* The electric force can be combined with any other forces acting on an object to find the [[183_notes: | * The electric force can be combined with any other forces acting on an object to find the [[183_notes: | ||
* The electric force can contribute to a [[183_notes: | * The electric force can contribute to a [[183_notes: | ||
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* [[https:// | * [[https:// | ||
- | === The electric force is a conservative force === | + | ==== The electric force is a conservative force ==== |
In addition to the general results above, the electric force is also a [[https:// | In addition to the general results above, the electric force is also a [[https:// | ||
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Two examples of conservative forces from mechanics include: the gravitational force and the spring force. It doesn' | Two examples of conservative forces from mechanics include: the gravitational force and the spring force. It doesn' | ||
- | === Two Point Charges === | + | ==== Two Point Charges |
- | {{ 184_notes: | + | [{{ 184_notes: |
As an example of electric force, we will talk about an electric dipole - two charges (one positive and one negative) located a small distance apart. For an electric dipole, we can find the electric force from the negative charge on the positive charge and vice versa. Starting with the electric force on the positive charge, we can write the general relationship: | As an example of electric force, we will talk about an electric dipole - two charges (one positive and one negative) located a small distance apart. For an electric dipole, we can find the electric force from the negative charge on the positive charge and vice versa. Starting with the electric force on the positive charge, we can write the general relationship: |