Circuits-Simple Circuits

Circuit

closed loop that allows electricity to continually flow

Direct current

current that always flows in the same direction

Electromotive force

used to refer to the voltage of a circuit

Electric current

quantified by measuring the amount of charge that flows past a point per second

Amperes

unit for current; coulombs per second; named after Andre-Marie Ampere

Electric force

fundamental force by which atoms communicate with each other

Electrocardiogram (EKG)

device that measures voltage across various parts of the body to measure a person’s heartbeat; visual output measures voltage versus time

Electronic pacemaker

device that routinely sends electrical pulses to maintain a heart’s constant rhythm

Electrophysiology

study of electricity of the human body

Ohm’s Law

way to measure a current; I=V/R

Resistance

quantity that resists the flow of current, measured in ohms (Ω); form of friction that charged particles experience as they flow through a circuit

Factors that affect resistance

conductive materials have low resistance, longer wire will have greater resistance, higher temperature causes greater resistance

Ohmic circuits

circuits that obey Ohm’s Law

Danger of voltage and current

large voltage causes charge to build up a lot of energy, but if very few charged particles move through that potential, very little energy is delivered; large voltage is only dangerous with high conductivity

Relationship between voltage and current

voltage creates the conditions for current, current is what actually affects you

Power

rate of energy change over time, measured in watts

Watt

one joule per second

Electron flow through wire

encounters friction which creates heat in the wire

Incandescent lightbulbs

tungsten filament inside heats up enough to glow yellow (2000 C)

Kilowatt-hour

3.6 million joules

Drift velocity of electrons

less than 1 mm/s; electrons are actually moving millions of meters per second, but they move randomly and bounce off each other so they don’t get very far

Power plants

when a switch is flipped, it sends a signal to the wires in your home to start moving; switches on an electric field to accelerate the electrons

Electron movement

when an electron moves, its electric field shifts, telling other electrons where it is and repelling them; information on electron position spreads at the speed of light

Proton movement

do not move around as much as electrons, but will jiggle more when electrons are flowing, increasing temperature

Superconductors

substances for which there is a point at which resistance becomes zero; used in machines requiring high currents; require extremely low temperatures