Series versus Parallel Circuits The Ultimate Battle!

KEY POINTS NEW VOCABULARY: –Resistance –Voltage –Ohm’s Law

RESISTANCE RESISTANCE = the tendency for a material to oppose the flow of electrons, changing electrical energy into thermal energy and light. All materials have some electrical resistance. Resistance is measured in Ohms ( 

RESISTANCE Examples: 1)Lightbulb -Electrons flow through the filament of the lightbulb and bump into the metal atoms that make up the filament. -Some of the electrical energy from the bumps turns into thermal energy. -Eventually the metal filament gets hot enough to glow, making the lightbulb light up! -Electric current loses energy as it moves through the filament because the filament tries to stop the flow of electrons (HIGH RESISTANCE!!!)

RESISTANCE Examples: 2) Copper wiring -Excellent to use in houses because it has low resistance to the flow of electrons -Less electrical energy is converted to thermal energy so there is more electrical energy to power the house! (LOW RESISTANCE) (LOW RESISTANCE) SAVE ENERGY! USE COPPER WIRES! SAVE ENERGY! USE COPPER WIRES!

Factors that affect resistance… SIZE OF WIRE –Electrons move more efficiently through thick wires (Thin wires have more resistance!) -The longer the wire the higher the resistance! TEMPERATURE -High temperatures are also linked with high resistance

VOLTAGE Voltage is like an electrical pressure that pushes charges from high to low levels! Voltage is measured in volts (V) Just like water flows from high to low levels, electrical charges do that too!

Ohm’s Law There is a relationship between current, voltage, and resistance. –Current = I and is measured in amps (A) –Voltage = V and is measured in volts (V) –Resistance = R and is measured in ohms (  Current = voltage I = V / R resistance V = IR

KEY POINTS Anything that is plugged into an outlet requires electrical energy! That energy is moved around in CIRCUITS! EX: Hair dryer 1. The dryer has to be plugged into the outlet to operate. 2.A generator at the power plant produces a voltage difference across the outlet that makes charges move when the circuit is complete. 3.The dryer and the house have wires that carry the current. 4.The dryer turns the electrical energy into thermal and mechanical energy. 5.You break the path of current in the circuit when you turn off the dryer or unplug it.

The Snowman Robber!

Types of Circuits! Two types of circuits: –SERIES –PARALLEL

SERIES CIRCUIT Current flows through ONE loop! The parts of a series circuit are wired one after another. The amount of current and voltage are the same through every part. When any part is disconnected, no current flows and the entire circuit goes out! Also called an OPEN CIRCUIT!

SERIES CIRCUIT Examples: –Flashlights –Holiday lights THINK, PAIR, SHARE… Where would a series circuit be inconvenient? Why?

SERIES CIRCUIT

PARALLEL CIRCUITS Parallel circuits have 2 or more branches for current to move through. The voltage is the same in each branch of the circuit, but more current flows through branches that have lower resistance.

Advantages to Parallel Circuits… When one part is disconnected, the current still flows through the other branches. Houses, cars, and most electrical systems use parallel wiring. THINK, PAIR, SHARE… Why do you think houses use parallel circuits?

Parallel Circuit In a parallel circuit the current flow splits up and goes to different parts of the circuit. If one bulb or appliance goes out, the rest stay on. All bulbs are equally bright.

PARALLEL CIRCUITS

COMPARE/CONTRAST SERIES –One loop of current –Same voltage everywhere –Same current everywhere –If one part is disconnected the whole circuit goes out –Used in lightbulbs! PARALLEL –2 or more branches of current –Same voltage everywhere –Current changes based on resistance –If one part is disconnected, the circuit still carries electricity to the other branches –Used in houses and cars!

COMPARE/CONTRAST