phys_CURRENTS & CIRCUITS

Electrode

rods in simple battery

Electrolyte

solution in which electrodes are submerged

terminals

part of electrodes (rods) that are not submerged in electrolyte (solution)

Current

the rate at which charge passes a given point per unit time

*ampere (units)

Conventional current

direction of motion of positive charges

actual current

direction of motion of negative charges - protons are fixed in place, so in most objects, this is the direction of current

Direct current (DC)

current at a steady rate; constant over time

Alternating current (AC)

current at an alternating rate; changes over time in a sineusodial pattern (looks like sine graph)

Drift velocity

very small, less than 1 m/ hour

charges start to move towards source of potential difference

Ohm's Law

Current is directly proportional to potential difference

I vs. V

Resistors

devices that control the amount of current in a circuit

resistance

voltage / current

V = IR

*directly proportional to length
*inversely proportional to cross-sectional area

Electric Power

P = IV
= V^2/R

Equivalent resistance

single resistor that could replace a group of resistors w/o changing the overall circuit

series connection

end-to-end placement of elements

*Req = simple addition for resistors
*Req = fractions for capacitors

Parallel connection

current is split into branches, each of which contains a SINGLE element

*Req = fractions for resistors
*Req = simple adding for capacitors

Voltmeter

measures potential difference between 2 points in a circuit

*must be wired in parallel
*resistance is ideally infinate

Ammeter

measures current (amperes) between two points in a circuit

*must be wired in series

multimeter

digital device that can measure both voltage and current

multimeter

digital device that can measure both voltage and current

Electromotive Force (emf)

MISNOMER! not actually a force.
another name for the potential difference across a battery or other source