Key Idea: Electrostatic potential energy can be stored in the separation of charged objects.
Students should know that:
- Because all charged objects (including atoms and molecules) exert a force on all other charged objects, whenever two charged objects are separated by some distance, the objects tend to move toward each other (in the case of two opposite charges) or move away from each other (in the case of two like charges). (If they do not move toward each other, it is because some other force equal to the force of attraction or repulsion acts to oppose their coming together or moving apart.) The energy the charged objects have due to their separation is called electrostatic potential energy.
- In cases where the charges are not allowed to move toward each other or away from each other (e.g. as in capacitors, which are oppositely charged conductors separated by a non-conducting (insulating) material), the electrostatic potential energy can be transferred electrically to power electrical devices.
- The electrostatic potential energy of a system of two charged objects depends on the magnitude of the charges on them and the distance between them.
- Increasing the magnitude of the charges increases the electrostatic potential energy, and decreasing the magnitude of the charges decreases the electrostatic potential energy.
- For objects that have like charges, the electrostatic potential energy increases as the distance between the charged objects decreases, and the electrostatic potential energy decreases as the distance between the charged objects increases.
- For objects that have opposite charges, the electrostatic potential energy increases as the distance between the charged objects increases, and the electrostatic potential energy decreases as the distance between the charged objects decreases.
Boundaries:
- Assessment items do not ask students to use formulas, such as U_{E} = (k_{e}q_{1}q_{2})/r or U_{E} = ½ CV^{2}, to calculate electrostatic energy. The sub-ideas above describe semi-quantitative relationships.
Item ID Number |
Knowledge Being Assessed | Grades 4–5 |
Grades 6–8 |
Grades 9–12 |
Select This Item for My Item Bank |
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46% | |||
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20% |
Misconception |
Student Misconception |
Grades 4–5 |
Grades |
Grades |
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N/A | 31% |
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19% |
Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.
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