Chapter 21: Electric Currents and Electric Circuits

series

one pathway

parallel

multiple pathways

if one lamp in a series burns out, the current...

stops flowing due to open circuit

if one lamp in a parallel burns out, the current...

stays the same

greater voltage drop

parallel

lines are overloaded

more than safe amount of current flowing through circuit

why can a bird perch without harm on a high voltage power line

it has a potential difference of zero/the potential difference across its feet remains the same

direct current

only going in one direction

alternating current

electricity moving in many directions

DC

battery

AC

generator

power

the rate of using energy

voltage

electrical potential energy/charge

electromotive force (emf)

potential difference/voltage

ohm's law

current is directly related to voltage

what is NEEDED for a circuit

voltage source, wires, resistors

schematic battery

schematic resistors

schematic switch

series

adding resistors lowers current

parallel

adding resistors makes current go up and resistance down

ammeter in a series

0 resistance-no effect on resistance or current

voltmeter in parallel

infinite resistance-no effect on resistance or current

voltmeter in series

circuit won't work

ammeter in parallel

short circuit-bypass other resistors

short circuit

-bypass normal R

-current goes way up

-resistance goes way down

overload

more than safe amount

fuse

meant to open circuit when something is wrong-melts

electrical current

the movement of a charged particle in an electrical field

conventional current

in the direction that a positive charge would move, and current will always flow until both ends are at an equal potential

diode

acts as an AC to DC converter

battery

uses a chemical reaction to set up a separation of charges that creates and electrical field, and thus a potential difference or voltage

electrical circuit

wire that directs the current in a specific path, the charges move around a closed loop

resistor

only allows a certain amount of current to flow

schematic diagram

uses standard symbols to better describe the pathways taken by the current and the voltages and resistances involved

series current

same everywhere

parallel current

-inversely proportional to resistance

-sum of currents in each branch will equal the current

series voltage drop

-directly proportional to resistor

-sum of voltage drop across all resistors equals total voltage available

parallel voltage drop

-same no matter where you measure in the parallel

-equal to current multiplied by equivalent resistance

series resistance

total resistance always greater than any single resistor

parallel resistance

-total resistance always less than any individual resistor

-same everywhere (equivalent resistance)

series general properties

-as number of resistors increase, current decreases

-if one resistor goes, current in the entire line stops

-fuses and circuit breakers are connected in series

-best for individual room or section wiring in a house

-ammeters connected

parallel general properties

-voltmeters connected

-if you lose one resistor, the rest keep working

-adding resistors will lower overall resistance and increase current

-best suited for whole house wiring