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Ch 19 Electricity
Question | Answer |
---|---|
The basic building blocks of matter | Atoms |
What are the three particles found in atoms and their charges | Protons (+), neutrons (0), and electrons(-) |
Which particles are found in the nucleus? | Protons and neutrons |
Where are electrons found? What are their charge | In the “electron cloud” outside the nucleus and they are negative |
Which is the only particle that moves freely? | Electrons, because they can be “knocked off” the outside of the atom, creating an electric charge. |
What causes an object to become negatively charged? | Electrons move from another object to that object |
What causes an object to become positively charged? | Electrons move to another object from that object |
A charged object is brought near another object or surface, producing an electric charge by charge separation (like the negative balloon sticking to the wall because the electrons move deeper into the wall making the surface of the wall positive...) | Charging by induction |
Two objects are brought into contact and negative charges move from one to the other, giving both a charge | Charging by conduction |
Electric charges that are the same do this | Repel |
Electric charges that are different or opposite do this | Attract |
What are the two types of electricity? | Static electricity and current. |
The build up of charges in one area due to the gain or loss of electrons is called this | Static Electricity |
What causes a spark (electric discharge) to “jump?” | The negative charges built up on one object (usually by conduction or friction) are attracted to a conductor with a lower concentration of negative charges. The electrons "jump" to get away from each other (like charges repel) |
The flow of electrons in a wire | electric current |
How do electrons behave in current electricity? | They “flow” through a conductor from an area of high negative charge to an area of low negative or positive charge. |
Materials like metals that allow electrons to flow easily through them | conductors |
Materials that resist the flow of electrons | insulators |
Name some conductors | Most metals, water with dissolved salts (ions), the human body, especially if wet |
Name some insulators | Plastic, wood, glass, rubber, distilled water, cloth, string... |
What example of electric current did we study? | A lit flashlight, bulb and battery, breadboard circuits |
What source of electric current ran the circuits build in lab? | a battery |
What do we call a large discharge of static electricity from cloud to cloud or cloud to ground? | Lightning |
What happens to clouds in a thunderstorm? | Circulating winds cause a build up of negative charges near the bottom of the cloud by friction (rubbing of ice or water molecules within the cloud) |
What happens to the ground and objects on the ground in a thunderstorm? | As charged clouds draw closer, negative charges move away from them, giving the surface of the ground/objects a positive charge (charging by induction) |
What is lightning? | A large discharge of static electricity from cloud to cloud or cloud to ground caused when negative charges “jump the gap” to a positively charged area. |
What do we call it when static electricity or other unwanted charges are directed into the earth through a conductor? In home wiring this happens through the third prong in a three prong plug and outlet. For lightning this is a lighting rod on a house . | Grounding |
What is the SI unit for measuring current? | Amps |
A closed loop that electric current flows through is a ______ | circuit |
A circuit with only one path (loop) for current to flow through is a ________. | Series circuit |
A circuit with more than one path for current to flow through (each device has its own path) is called a _____. | Parallel circuit |
What is one example of a series circuit? | Older Christmas lights (when one bulb goes out, the whole string won't light), one room of a house |
How are most houses wired today? | The rooms are wired in parallel, but each room is series |
Name some household safety devices. | Fuses, circuit breakers, grounded outlets |
What does a closed circuit require for current to flow? This is the "pump" that pushes electrons through the wire. | A Voltage difference |
The difference in potential electric energy, or electrons, between two areas that creates the push to move charges in a circuit. | voltage |
In SI, what is the unit for Voltage? | Volt |
What creates the voltage difference found in wall outlets? | The generator at a power plant provides the "push" that we use to run electric appliances by spinning a magnet in a coil of wire at a generator. It makes AC or alternating current. |
Opposition to the flow of current in a circuit is called ______. | Resistance |
What is the SI unit for resistance? | Ohms. (The ohm symbol resembles an upside-down horseshoe) |
What does resistance tend to produce? | Heat and/or light |
What is the difference between AC & DC? | DC (direct current) flows in one direction, like from a battery; AC (alternating current) switches directions many times per sec. AC is made by a generator. |
What have we studied that uses direct current? | A flashlight (powered by a battery or solar cell), our breadboard circuit kits |
What type of current is found in our homes? | Alternating current |
How can you be safe in a lightning storm? | Get inside a car or building, if outside stay away from tall things like trees or metal conductors, if you are the tallest thing around - crouch down on your tip toes (do not lay on the ground) |