STEM_5.6B_2.0_Explain_STEMscopedia

Circuits and Electricity

5.6B

energy: the ability to

do work

mechanical energy:

energy that an object has

because of its motion or

position

Have!you!ever!thought!about!how!much!we!depend!on!

electricity?!Electricity!is!a!form!of!energy&that!

runs!computers,!appliances,!and!radios.!

Electricity!lights!our!homes,!schools,!and!

office!buildings.!Without!it,!our!world!would!

be!a!much!different!place.!In!fact,!before!electricity!was!

discovered,!people!mainly!used!fire!to!cook!and!to!provide!light!

and!heat.!!

Electricity!has!become!an!important!part!of!our!lives.!You!might!

know!that!the!use!of!electricity!often!involves!wires.!But!how!do!

you!think!electricity!travels!through!these!wires?!How!does!it!

produce!other!kinds!of!energy!like!light,!heat,!and!sound?!

How&does&electricity&travel?&

All!matter!is!made!up!of!particles.!Electrical)energy!is!energy!produced!by!the!movement!of!

certain!particles.!This!flow!of!particles!is!called!electric)

current.!

So!what!does!this!have!to!do!with!lights,!appliances,!and!

computers?!In!order!to!light!a!light!bulb!or!turn!on!a!

computer,!we!need!to!produce!a!continuous!electric!

current.!To!do!this,!we!need!an!energy!source.!Common!

energy!sources!include!batteries!and!generators.!You’ll!

learn!more!about!these!shortly.!An!electric!current!also!

needs!a!path!along!which!it!can!travel.!An!electric)circuit!is!

a!pathway!through!which!electric!current!flows.!!

Now!you!know!that!electric!current!flows!through!a!path!called!a!circuit.!You!also!know!that!a!

continuous!electric!current!needs!an!energy!source!such!as!a!battery.!What!else!is!needed!to!

make!a!circuit?!

What&is&necessary&to&have&energy&flow&through&a&circuit?&&

You!can!think!of!a!circuit!as!a!loop.!In!order!for!electric!current!to!flow!through!the!loop,!the!

loop!must!not!contain!breaks.!In!other!words,!the!circuit!must!

be!closed.!An!open!circuit!has!one!or!more!breaks.!Most!

circuits!have!an!energy!source,!wires,!a!load,!and!a!switch.!As!

mentioned,!energy!sources!for!circuits!include!generators!and!

batteries.!Generators!are!machines!that!convert!mechanical&

energy!into!electric!energy.!In!this!lesson,!we’ll!focus!on!batteries.!Inside!a!battery,!two!kinds!of!!

Electric!current!flows!through!an!

electric!circuit!like!this!one.!!

Circuits and Electricity

5.6B

sound energy: energy

produced by vibrations

light energy: a visible

energy source

heat energy: energy of

moving particles in a

substance; also called

thermal energy

metals!build!up!opposite!charges.!Negative!charges!build!up!on!one!end!of!the!battery.!Positive!

charges!build!up!on!the!other!end!of!the!battery.!This!is!why!batteries!are!marked!with!a!

positive!sign!(+)!and!a!negative!sign!(–).!Electrons!are!attracted!from!one!end!of!the!battery!to!

the!other.!Connecting!these!two!ends!allows!an!electric!current!to!flow!between!them.!!

Wires!provide!a!path!through!which!current!can!flow!from!one!

end!of!a!battery!to!the!other.!Wires!are!made!from!materials!

that!carry,!or!conduct,!electrons!more!easily!than!other!

materials.!Materials!that!conduct!electrons!easily!are!called)

conductors.!Copper!and!aluminum!are!good!conductors.!Wires!

are!wrapped!with!a!material!called!an!insulator.!This!material!

does!not!easily!carry!electrons.!Insulators!keep!the!conductors!

inside!a!wire!from!touching!each!other!and!interrupting!the!

flow!of!electrons.!Rubber,!plastic,!and!glass!are!good!

insulators.!!

Circuits!deliver!electrical!energy!to!a!load,!or!device,!that!will!

use!that!energy.)Loads!change!electrical!energy!into!some!

other!form!of!energy.!

Light!bulbs,!fans,!and!

buzzers!are!common!

loads.!Think!about!a!

light!bulb.!When!

current!passes!through!

the!wires!inside!the!bulb,!

electrical!energy!changes!

into!heat&energy!and!

light&energy.!Similarly,!

when!current!passes!

through!a!buzzer,!electrical!energy!changes!into!sound&energy.!!And!when!current!passes!

through!a!fan,!electrical!energy!changes!into!mechanical!energy.!!

All!parts!of!a!circuit!must!be!connected!in!order!for!current!to!flow!through!the!circuit.!The!

picture!on!the!left!shows!a!switch,!which!is!a!device!that!closes!and!opens!a!circuit.!A!switch!

connects!or!separates!two!pieces!of!metal.!When!the!metal!pieces!are!connected,!the!circuit!is!

closed.!Electrons!can!flow!through!the!circuit.!When!the!metal!pieces!are!separated,!the!circuit!

is!open.!Electrons!cannot!flow!through!the!circuit.!Loads!do!not!function!in!open!circuits!

because!the!current!does!not!pass!through!them.!For!example,!a!light!bulb!will!not!light!up!in!

an!open!circuit.!!

This!electric!cord!is!made!of!three!

insulated!c o p p er !w ire s.!T h e!a rr o w !

is!pointing !to !th e!in s u la to r!th a t!

protects!all!three!wires.!!

Circuits and Electricity

5.6B

Remember!that!energy!is!not!created!in!an!electric!circuit.!When!electricity!produces!

light!in!a!light!bulb!or!sound!in!a!buzzer,!energy!is!simply!changing!forms.!!

Look!at!the!photographs!above.!The!photograph!on!the!left!shows!a!radio!speaker.!

The!center!photograph!shows!a!roll!of!aluminum!foil.!The!photograph!on!the!right!

shows!a!rubber!band.!Think!about!how!each!object!could!be!used!in!a!circuit.!Then!

decide!whether!each!one!would!best!be!used!as!a!

conductor,!an!insulator,!or!a!load.!

With!a!few!different!materials,!you!can!explore!the!parts!of!

a!circuit.!Flowing!electrons!can!cause!a!shock!if!you!come!

into!contact!with!them,!so!it’s!always!good!practice!to!

handle!electricity!with!care.!Be!sure!to!use!caution!when!!!handling!

the!exposed!parts!of!the!wires.!!

1. You!will!need!a!battery!holder!and!a!battery.!You!will!also!need!

two!pieces!of!insulated!wire!with!exposed!ends,!a!light!bulb!

holder,!and!a!light!bulb.!!

2. Connect!the!battery!holder,!wires,!and!bulb!holder!as!shown!in!the!diagram!on!the!right.!

Describe!your!observations.!!

3. Now!insert!the!light!bulb!into!its!holder.!Describe!your!observations.!!

4. Insert!the!battery!into!its!holder.!Make!sure!the!positive!(+)!and!negative!(–)!ends!of!the!

battery!match!the!positive!(+)!and!negative!(–)!markings!on!the!holder.!Describe!your!

observations.!!

5. Disconnect!an!end!of!one!of!the!wires!from!the!light!bulb!holder.!What!happened!and!why?!

Circuits and Electricity

5.6B

magnetism: the force of

pulling or pushing between

poles, or ends, of a magnet

magnetic field: the area

around a magnet that is

affected by magnetic forces

6. If!you!placed!a!piece!of!aluminum!somewhere!within!the!circuit!and!the!circuit!

remained!closed,!would!the!light!bulb!still!light?!What!would!happen!if!you!

placed!a!piece!of!rubber!within!the!circuit?!Explain.!!

)

Getting&Technical:&Electromagnets&

Electricity!and!magnetism!are!closely!related!because!both!involve!negative!and!positive!

charges!in!matter.!In!fact,!when!electric!current!flows!through!a!

conductor,!it!generates!a!magnetic&field!around!the!conductor.!The!

magnetism!resulting!from!flowing!electric!charges!is!called!

electromagnetism.!!

You!can!increase!the!strength!of!a!magnetic!field!in!a!current[

carrying!wire!by!wrapping!the!wire!to!form!coils,!or!loops.!The!more!

coils!you!have,!the!stronger!the!magnetic!field.!To!make!an!even!

stronger!magnetic!field,!you!can!wrap!the!coils!around!an!iron!rod!

(or!other!iron!object).!The!current!passes!through!the!wire!coils!

and!magnetizes!the!rod.!This!produces!a!strong!magnet!called!an!

electromagnet.!Many!everyday!devices!use!electromagnets,!

including!doorbells!and!electric!motors.!

A!copper!wire!is!wrapped!around!an!iron!

nail!in!this!electromagnet.!The!letters!

“N”!and!“S”!indicate!the!north!and!south!

poles!of!the!magnetic!field.!!!

Circuits and Electricity

5.6B

What&Do&You&Know?!

The!flow!of!electricity!depends!on!an!energy!source!and!a!path,!or!circuit,!through!which!it!can!

travel.!Study!the!images!below.!Decide!whether!or!not!electricity!will!completely!flow!through!

each!circuit.!Write!“yes”!or!“no”!in!the!space!below!each!image,!and!explain!your!reasoning.!

Then,!for!each!image!that!includes!the!answer!“yes,”!describe!the!form!of!energy!produced!by!

the!electricity.!!

Circuits and Electricity

5.6B

Circuits&and&Electricity&at&Home&

To!help!students!learn!more!about!circuits!and!electricity,!go!

through!each!room!of!your!living!space!and!have!students!make!a!list!of!

all!the!devices!that!use!electrical!energy.!Discuss!the!different!forms!of!

energy!that!are!produced,!and!have!students!find!the!switches!on!each!

device!if!applicable.!For!example,!a!computer!uses!electricity!to!produce!

light!(through!the!monitor)!and!sound!(thorough!the!speakers).!If!you!touch!the!monitor!or!

outside!of!the!hard!drive,!you!will!probably!also!feel!thermal!energy.!Many!computers!have!

three!switches:!one!for!the!monitor,!one!for!the!speakers,!and!one!for!the!hard!drive,!which!

controls!the!computer!as!a!whole.!!

If!possible,!take!students!to!the!area!of!your!living!space!that!houses!the!fuse!box!or!circuit!

breaker!panel.!A!fuse!box!or!circuit!breaker!panel!is!basically!the!distribution!center!for!all!of!

the!electric!circuits!in!your!home.!A!utility!company!provides!the!main!source!of!electricity,!

which!flows!through!an!electric!meter!that!tracks!usage.!Then!the!electricity!eventually!flows!

through!the!fuse!box!or!circuit!panel.!The!breakers!or!switches!control!the!electricity.!If!too!

many!devices!on!the!same!circuit!are!used!at!the!same!time,!an!overload!may!occur.!If!there!is!

an!overload!of!electricity!in!any!of!the!circuits!of!the!home,!the!breaker!will!open!the!circuit!to!

stop!the!flow!of!electricity.!Explain!to!students!that!this!is!a!safety!feature!to!help!prevent!

electrical!fires.!

Here!are!some!questions!to!discuss!with!students:!

• Where!do!you!think!the!circuits!are!located!in!each!device!you!listed?!

• What!would!happen!to!a!device!if!part!of!the!circuit!were!missing!or!broken?!

• If!you!have!problems!with!electrical!circuits!in!your!home,!you!might!call!an!electrician.!

What!kind!of!information!do!you!think!an!electrician!needs!to!know!in!order!to!do!his!or!

her!job?!