Question

gravity/electricity/magnetism - study guide• know the following terms and examples:○ conductor (and examples)○ insulator (and examples)○ electric charge (when is it strongest?)○ static electricity○ current electricity○ magnetic field○ magnetic domain○ magnetic poles○ electromagnet○ generator○ electric motor○ electromagnetic induction○ gravity• how are atoms electrically neutral?• when do objects repel? when do they attract?• what are the 3 ways to electrically charge an object? give examples of each.• what happens when a magnet is broken into smaller pieces?• where is the magnetic field the strongest on a magnet?

Explanation:

Key Terms & Examples

1. Conductor: Material that allows electric current flow easily; outer electrons are loosely held.
2. Insulator: Material that blocks electric current flow; outer electrons are tightly held.
3. Electric charge: A property of matter that causes electrostatic force; strength depends on distance (Coulomb's law: force is inversely proportional to the square of distance between charges).
4. Static Electricity: Buildup of stationary electric charge on an object, from electron transfer.
5. Current Electricity: Flow of electric charge (usually electrons) through a conductor.
6. Magnetic field: Invisible region around a magnet where magnetic force acts on magnetic materials or moving charges.
7. Magnetic domain: Tiny regions in ferromagnetic materials where atomic magnets align uniformly.
8. Magnetic poles: The two ends of a magnet (north and south) where magnetic force is strongest; poles always exist in pairs.
9. Electromagnet: A temporary magnet made by running electric current through a coil of wire around a ferromagnetic core; strength depends on current and coil turns.
10. Generator: Device that converts mechanical energy to electrical energy using electromagnetic induction.
11. Electric motor: Device that converts electrical energy to mechanical energy using magnetic forces on current-carrying wires.
12. Electromagnetic induction: The process of generating an electric current by moving a conductor through a magnetic field (or changing the magnetic field around a conductor).
13. Gravity: A fundamental force of attraction between all objects with mass; weakest of the fundamental forces, but acts over infinite distance.

Specific Questions

1. Atomic electrical neutrality: Atoms have equal numbers of positively charged protons (in the nucleus) and negatively charged electrons (in electron clouds), so their total charge cancels out.
2. Object attraction/repulsion: Charged objects repel when they have identical electric charges (positive-positive or negative-negative); they attract when they have opposite electric charges (positive-negative). Neutral and charged objects also attract due to charge induction.
3. 3 ways to charge an object:

• Friction: Transfer electrons by rubbing two different materials together.
• Conduction: Transfer electrons by touching a charged object to a neutral conductor.
• Induction: Redistribute electrons in a neutral object by bringing a charged object near it (no direct contact).

1. Broken magnet: Each smaller piece becomes a complete, smaller magnet with its own north and south magnetic pole; magnetic domains reorient to form new pole pairs in each fragment.
2. Strongest magnetic field: The magnetic field is strongest at the magnetic poles (the north and south ends) of the magnet, where magnetic field lines are most densely packed.

Answer:

Key Terms & Examples

1. Conductor: Examples include copper, aluminum, silver, and saltwater.
2. Insulator: Examples include rubber, plastic, glass, and dry wood.
3. Electric charge: It is strongest when the distance between two charged objects is smallest.
4. Static Electricity: Example: A balloon sticking to a wall after being rubbed on hair.
5. Current Electricity: Example: The flow of electricity through the wiring in a home to power lights.
6. Magnetic field: Represented by lines that run from the north pole to the south pole outside a magnet.
7. Magnetic domain: In an unmagnetized nail, domains are randomly oriented; in a magnetized nail, domains align.
8. Magnetic poles: All magnets have a north-seeking pole and a south-seeking pole; opposite poles attract, like poles repel.
9. Electromagnet: Example: The magnets used in scrap yards to lift metal objects, which turn off when current stops.
10. Generator: Example: The generators in a power plant that use steam to spin turbines and create electricity.
11. Electric motor: Example: The motor in a household fan that spins the blades when powered.
12. Electromagnetic induction: This is how a bicycle dynamo generates electricity to power the bike's light when the wheel spins.
13. Gravity: Example: The force that keeps planets in orbit around the Sun and pulls objects toward Earth's surface.

Specific Questions

1. Atoms are electrically neutral because they have an equal number of positively charged protons and negatively charged electrons, so their charges balance out.
2. Objects repel when they have the same type of electric charge (positive-positive or negative-negative). Objects attract when they have opposite electric charges (positive-negative), or when a charged object interacts with a neutral object (via charge induction).
3. The 3 ways to charge an object are:

• Friction: Rubbing a glass rod with a silk cloth (the glass loses electrons and becomes positively charged, the silk gains electrons and becomes negatively charged).
• Conduction: Touching a neutral metal spoon to a positively charged metal plate (electrons from the spoon move to the plate, making the spoon positively charged).
• Induction: Bringing a negatively charged balloon near a neutral metal can (electrons in the can are repelled to the far side, making the near side of the can positively charged; the can can be grounded to trap the charge).

1. When a magnet is broken into smaller pieces, each piece becomes a fully functional, smaller magnet with its own distinct north and south pole.
2. The magnetic field is the strongest at the north and south poles (the ends) of the magnet.