# Dickey Physics ch. 22-23

## 42 terms

### electric current

a flow of charged particles

### conventional current

flow of positive charges

### Alessandro Volta

discovered a much better way of producing electric currents than using short-lived discharge devices

### pile

metals in pairs, called cells, in a vertical arrangement

### battery

a device made up of several galvanic cells connected together; converts chemical energy to electric energy

### direct (DC)

current which flows through the wires of the circuit from the positive side of the battery to the negative side

### alternating (AC)

current that alternates in direction

### electric circuit

forms when charges move around in a closed loop

### generator

converts kinetic energy into electric energy

unit of power

unit of current

### ammeter

device that measures current

### resistance (R)

the property which determines how much current will flow

### ohms

unit of resistance

### Georg Ohm

formulated the concept of resistance and discovered the proportionality

### Ohm's Law

states that the resistance is constant over a wide range of applied voltages (potential differences)

V = IR

### ohmic

materials that obey Ohm's law (at least over a range of coltages)

### resistor

a conductor that provides a specified resistance in an electrical circuit; often used to control the amount of current flowing in a circuit or part of a circuit

### superconductor

materials with no resistance; can conduct electricity without loss of energy

### potentiometer

a variable resistor

### lamp

converts electric energy into light energy

### motor

converts electric energy into mechanical energy

### joule heating loss

unwanted thermal energy

### open circuit

occurs when the path is not complete and charge will not flow and the current stops

### short circuit

occurs when a voltage source has a low resistance path to the ground; the result is a very large current flow and the wires can overheat

### circuit schematic

an electric circuit drawn using standard symbols for the circuit elements

### series

the simplest circuit where the conductors, resistors, and power source are connected with only one path for current

### series connection

where there is only one current path

### parallel

formed when two or more resistances are placed in a circuit side by side so that current can flow through more than one path; the same voltage is applied across each branch

### voltmeter

a device used to measure the potential difference between two points

### parallel connection

where the circuit component and the voltmeter are aligned parallel to each other

### series-parallel

circuit with some components in series and others in parallel; the power source and control or protection devices are usually in series while the resistors are usually in parallel; the same voltage is applied to parallel devices and different voltages to series devices

### voltage drop

the voltage across a resistor

### Kirchoff

formulated a law which states that the sum of voltage drops across the resistances of a closed circuit equals the total voltage applied to the circuit

### compound circuits

another name for series-parallel circuits; require at least three resistors to be formed

### fuse

a short piece of metal that melts when too large a current passes through it

### circuit breaker

an automatic switch that opens when the current reaches a threshold value

### ground fault circuit interruptor (GFCI)

a fast-acting circuit breaker that senses small imbalances in the circuit caused by current leakage to the ground then shuts off the electricity; used near water because the body's resistance drops when wet

### arc fault

the flow of electricity over an unintended path

### arc fault circuit interruptor (AFCI)

a device that protects your home by detecting dangerous arcs and safely de-energizing the circuit

### equivalent resistance

the value of a single resistor that could replace all resistors in a circuit without changing the current

### parallel circuit

used in electric wiring at home