Electricity Chapter 11
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Electrical Current
A closed path which electrons that are powered by energy can flow.

Voltalic Cell
A source of energy that generates an electric current by chemical reactions involving two different metals or metal compounds separated by a solution that is a conductor.

Battery
A connection of two or more cells.

Electrode
 One of the two metal terminals on a cell or battery
 The breakdown of an electrode is one factor that can limit the life of a cell

Electrolyte
A solution or paste that conducts charge.

Dry Cell
A cell that contains an electrolyte which is a paste.

Wet Cell
A cell that contains a liquid electrolyte.

Primary Cell
A cell that can only be used once.

Secondary Cell
A cell that can be recharged.

Fuel Cell
 A cell that can generate electricity through the reactions of fuel stored outside of the cell
 Hydrogen fuel cells combine hydrogen that is stored in a tank or cartridge with oxygen from the air
 Byproducts are heat and water

Solar Cell
A cell that converts sunlight into electrical light.

Terminal
A position on a cell that must be connected to other components to form a circuit.

Switch
 Controlled device
 Conductor that can complete or break a circuit

Open Circuit
Electrons cannot flow through any circuit with a gap or break (switches create these gaps).

Electrical Current
 The rate of movement of an electric charge
 In a circuit it is due to the flow of electrons

Coulomb (C)
 The unit of electric charge
 1 C = 6.25 x 10^{18} electrons

Ampere (A)
 The unit of electric current
 1.0 A means that 1.0 C of charge pass a given point in a circuit every second

Electrical Resistance
 Free electrons in a solid move when an electric field is produced by a cell
 Collisions (with ions or other electrons) interfere with the flow of electrons
 It is a property of a substance that hiders electric currents and converts electrical energy into other forms
 Metals have lower resistances and that is why they are used as wires to make circuit conductors

Resistor
A device used in an electrical circuit to decrease the current through a component by a specific amount.

Load
A resistor or any other device that transforms electrical energy into heat, sound, light or motion.

Potential Difference (Voltage)
 The voltage of a cell is related to the amount of work that is done on each coulomb of charge that moves between the terminals of the cell
 V = J/C

Volt
 The unit for potential difference
 Equal to 1 J/C
 Electrons move from the negative terminal through the circuit to the positive terminal
 A voltmeter is used to measure potential difference
 Electrical charge does not lose energy as it moves along a perfect conductor with no resistance

Circuit Diagram
 A diagram that sues standard symbols (refer to notes) to represent components in an electric circuit
 You must include: the direction the electrons travel, the positive and negative terminals, voltage

Series Circuit
A circuit in which there is one path for the electrons to flow through.

Parallel Circuit
A circuit in which there are multiple paths for the electrons to flow through.

Ohm's Law
 The ratio of potential difference (V) to current (I) is a constant called resistance (R)
 V=IR
 Can be rearranged to find current (I=V/R)
 Can be rearranged to find resistance (R=V/I)
 Larger resistance=smaller current
 Unit for resistance is an Ohm

Ohm
 The unit for resistance
 Refer to image in previous question

Superconductor
A material in which electric charge can flow with no resistance.

NonOhmic
Something that does not follow Ohm's Law

Loads in Series (LS)
Refer to: LS Current, LS Potential Difference, LS Resistance, Decreased Current=Decreased Glow.

Loads in Parallel (LP)
Refer to: LP Current, LP Potential Difference, LP Resistance, Bulbs in Parallel.

LS Current
 The same at al points because there is only one path for the charge to flow
 I_{t}=I_{1}=I_{2}=I_{3}

LS Potential Difference
 The potential difference splits up because the energy has to be shared by all the loads but the sum is equal to what the power supply can provide
 If all loads are identical, potential difference will be shared equally; if unidentical more energy will go to the load with more resistance
 V_{t}=V_{1}+V_{2}+V_{3}

LS Resistance
 Adding more loads in a series is similar to adding more length to the wire
 More loads=more resistance
 Total resistance is equal to the sum of resistance in each load
 R_{t}=R_{1}+R_{2}+R_{3}

Decreased Current=Decreased Glow
 As more bulbs are added in series, each bulb will glow less because resistance will increase causing the current to decrease
 If the bulbs are identical they will glow the same
 If one bulb goes out, they all go out

LP Current
 The current will split up because there is more than one path for the electric charge to flow
 If all loads are identical the current will split up equally;if unidentical then the current will travel down the path with less resistance
 I_{t}+I_{1}+I_{2}+I_{3}

LP Potential Difference
 The potential difference is the same down each path on a parallel circuit because the electrons follow different paths but they only have to pass on energy to one load/path (at our level)
 V_{t}=V_{1}=V_{2}=V_{3}

LP Resistance
 Adding more loads in a parallel circuit is similar to having two straw to drink out of instead of one; more paths=less resistance
 Total resistance is less than the resistance down each path
 R_{t}<R_{1};Rt<R_{2};Rt<R_{3}

Bulbs in Parallel
 As identical bulbs are added in parallel the brightness of the bulbs remains the same because each path receives the same amount of energy
 One goes out, all stay on