| Topic 10.1 Electric Charge and Electric Force | |
| Skill | Resource |
| Visualizing Equipotential Lines | Noragulfa.com E-Field Explorer |
| Topic 10.2 Conservation of Electric Charge And the Process of Charging | |
| TOPIC 10.3 Electric Fields | |
| Skill | Resource |
| Drawing E-field vectors | fysicsfool video |
| Topic 10.6 Capacitors | |
| Skill | Resource |
| Understanding how capacitors behave | PhET Capacitor Lab Basics |
Concepts in Unit 10
- “charge” is the name we give to the property of matter that causes matter to exhibit the electric force
- everyday (macroscopic) objects have large and equal amounts of positive and negative charge, until something happens to transfer charge
- the reservoir of positive charge in the atoms of objects are the protons in the nucleus
- protons stay in the same average position in solids
- the reservoir of negative charge in macroscopic objects is the electrons in the electron cloud
- electrons can shift position while remaining “attached” to a nucleus, or they can be transferred
- in scenarios with macroscopic objects, charge doesn’t transfer unless there is contact, or a spark occurs (air is a good insulator, a spark occurs when air breaks down)
- the total amount of charge in any process is always constant
- when an initially neutral object becomes frictionally charged, one object gains a negative charge, and the other object gains an equal positive charge
- electrons are able to move freely in conductors
- electrons may be displaced in insulators
- diagrams of charging processes show excess charge
- a neutral object can interact electrostatically when charge is slightly displaced in the object
- grounding connects an object to a source or a sink for excess charge (electrons may travel to or from ground)
- long-distance forces can be explained with the field concept
- the electric field is the ratio of the electric force at a point in space for every one unit of positive charge
- the electric potential is a measure of the electric potential energy for every one unit of positive charge
- electric field and electric field lines are defined for a positive test charge; this is why electric field lines point away from positive charges
- electric field may be mapped with individual vectors or field lines
- electric field vectors are always tangent to electric field lines
- electric potential may be mapped with lines of equal potential, called “equipotential lines” or “isolines”
- electric field vectors are always perpendicular to equipotential lines and point towards lower potential (the positive test charge definition again)
- electric potential behaves like topography; moving to higher potential transfers energy and corresponds to moving to higher elevations
- capacitors are devices for storing electric potential energy
- a single capacitor plate may have an excess charge, but a capacitor at equilibrium has a net charge of zero
- the electric field is uniform between the plates of a capacitor; the force on a particular charge in a uniform field is always the same
- a dielectric (insulating) material inserted between the plates of a capacitor weakens the electric field inside of a capacitor and increases the amount of charge stored on a capacitor plate
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