physics prelim

NEUTRAL

Objects containing an equal number of electrons and protons.

electrically charged

An object with an imbalanced number of protons and electrons.

ELECTRICITY

• Occurs when electrons move from one atom to another
• The flow of electric charge

ELECTRIC CURRENT

• The continuous flow of electric charge through a conductor or space
• Typically carried by electrons in a wire

ELECTRONS

• Loosely held in many materials
• Can move freely
• Primary carrier of electricity in solids
• Negatively charged

NEGATIVE CHARGE

→ an object with more electrons than protons

POSITIVE CHARGE

→ an object with more protons than electrons

STATIC ELECTRICITY

• Build-up of electric charge on the surface of an object
• Happens when electrons are transferred by friction

CURRENT ELECTRICITY

• Continuous flow of electrons through a conductor
• Happens when a power supply creates a force that pushes electrons to move in one direction

ELECTRIC CHARGE

• A fundamental property of matter that causes particles to experience electric forces:
⚬ attraction
⚬ repulsion

• Atoms contain charged particles

LAW OF ELECTRIC CHARGES

• Explains how charged objects interact with each other

⚬ Electric charge is a conserved quantity
⚬ Charge cannot be created or destroyed, but it can be transferred between objects

Repel

R1: Like Charges ????
⚬ Two positive (+) charges
⚬ Two negative (−) charges

Attract

R2: Opposite Charges ????
⚬ A positive (+) charge and a negative (−) charge

ELECTRIC FIELD

• The region around a charged object where it exerts an electric force on other charges
• A charge creates a field around it
• Another charge entering that field feels a force

POLARIZATION

• Redistribution of electric charges in a neutral object when placed near a charged object

Charges in the neutral object shift slightly:
⚬ Electrons move toward a positive external charge
⚬ Electrons move away from a negative external charge
⚬ Creates opposite charges on different sides of the neutral object

• Attraction occurs even though the object is neutral

CONDUCTORS

• A material that allows electric charges (electrons) to flow freely through it

Characteristics:
• Electrons are loosely bound and can move easily
• Low resistance to electric current
• Often metals

Uses:
• Electrical wiring | Circuit components | Electrical contacts

Like: Copper, Gold, Graphite, Water

INSULATORS

• A material that does not allow electric charges to move freely

Characteristics:
• Electrons are tightly bound to atoms
• High resistance to electric current
• Often non-metals

Uses:
• Covering wires | Handles for electrical tools

Like: Wood, Fabrics, Ceramics, Glass, Plastics

Charles-Augustin de Coulomb

ELECTROSTATIC FORCE = ELECTRIC FORCE

• Proposed by French physicist

• Formulated the equation of electrostatic force
• Described the repulsive force between like charges and attractive force between opposite charges
• Explained how electric charge spreads on conductors

CONDUCTION

• Occurs when two materials are in direct contact, causing their atoms to collide
• Some electrons move from one material to the other
• Results in electron transfer and static charge buildup

HEAT TRANSFER: yes
ELECTRON MOVEMENT: yes

CONVECTION

• Involves the bulk movement of fluids (air or liquid), not electrons
• Electrons do not transfer between objects
• Any charge transfer is negligible; convection mainly moves heat, not electrons

HEAT TRANSFER: yes
ELECTRON MOVEMENT: no

RADIATION

• Transfers energy through electromagnetic waves
• No electrons move between objects
• Electrons within atoms may vibrate more due to absorbed radiation, but they remain bound

HEAT TRANSFER: yes
ELECTRON MOVEMENT: no

INDUCTION

• A charged object brought near another object causes electrons to rearrange
• No physical contact occurs
• Electrons shift position within the object, but do not transfer unless grounding occurs

HEAT TRANSFER: negligible
ELECTRON MOVEMENT: no (unless grounded)

DIRECT CURRENT

Continuous flow of electrons in one direction along a straight path

ALTERNATING CURRENT

The direction of electron flow periodically reverses

STATIC CURRENT

Accumulation of electric charges on the surface of an object, not a continuous flow

LIMITING CURRENT

Maximum safe or practical threshold for current flow in a system or component

Electrons

Type of subatomic that : Charged particles directly involved in generating electric current

Protons

Type of subatomic that do not flow to create current; immobile in solid conductors

Neutrons

Type of subatomic that do not carry charge and do not generate electric current

Voltage

• Supplies the needed push on electrons to produce current in an electrical circuit

• Pushes electrons to move from the cell’s positive terminal to the negative terminal

Current

• (I)

• The flow of electrons through a conductor per unit time

Power

The rate at which work is done or energy is transferred in a circuit

• P=W/t​

• P=V×I

Work

• The energy transferred by the electric current when moving electrons through a potential difference

Formula: W=V×I×t

ELECTRIC CIRCUIT

• A complete and unbroken pathway for electric current to flow

Power Source

• Provides the energy for current to flow
• Examples: battery, wall outlet

Load

• • A device that uses electrical energy
  • Examples: light bulb, motor, computer

Switch

Can open or close the circuit to turn electricity on or off

Resistor

Regulates (limits) current in a circuit
• Protects the system from excessive current (e.g., short circuit)

Capacitor

A passive electronic component that stores electrical energy in an electric field between two conductive plates separated by an insulator (dielectric)

Series Circuit

Components connected one after another in a single loop

Parallel Circuit

Components connected side-by-side, each on its own path

Series-Parallel Circuit

Combination of both series and parallel connections