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Circuits and Electrical Current Circuits and Electrical Current

Circuits and Electrical Current - PowerPoint Presentation

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Uploaded On 2018-09-21

Circuits and Electrical Current - PPT Presentation

Essential Questions for Circuits What are the requirements of a circuit What is actually going on in a working circuit What variables affect what other variables in a circuit What laws and formulas govern the relationships between these variables ID: 673969

bulb circuit water current circuit bulb current water potential difference battery resistance park loop wires bulbs relationship variable analogy

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Slide1

Circuitsand Electrical CurrentSlide2

Essential Questions for Circuits

What are the requirements of a circuit?

What is actually going on in a working circuit?

What variable(s) affect what other variable(s) in a circuit? What law(s) and formulas govern the relationship(s) between these variables?

What are the different kinds of circuits? How do they differ (design and use)?Slide3

Incandescent bulb:Slide4

How do you make a circuit?

You will be given one bulb, one battery and more than enough wires.

Construct a sketch of how wires can be connected to light a bulb.

Test your design. If it doesn’t work, try variations.

Record your working design(s)

Summarize the requirements of a functioning circuit.Slide5

The Requirements of a CircuitSlide6

The Requirements of a CircuitSlide7

What do you already know?Slide8

The Basic Function of a CircuitSlide9

What is “really” happening in the circuit?

Go onto

Phet

, Circuit Construction Kit (DC Only) Virtual Lab

Build a circuit with one bulb, one battery, one switch, and as many

wires as you

need to make the circuit show you clearly what is happening when the switch is closed.

What do the moving balls represent? Which way do they move?Slide10

What is “really” happening in the circuit?

The balls represent electrons – obviously NOT shown to scale.

The electrons move from negative on the battery, around to positive.Slide11

A Useful Analogy

Sometimes, a closed conducting loop (circuit) is compared to a water (amusement) park. Complete this analogy:

Water Park

Circuit

pump

electrons

pipes

bulb Slide12

A Useful Analogy

Sometimes, a closed conducting loop (circuit) is compared to a water (amusement) park. Complete this analogy:

Water Park

Circuit

pump battery

water electrons

pipes wires

slide/obstacles bulb Slide13

Practice

Answer CYU #1,2 on PCR Lesson 2b. Slide14

Electric Potential Difference

What is it?

What are its units?

How do we measure it?

Is it “the cause” or “the effect” in a circuit?

Read 1b,c

Start your word webSlide15

Electric Potential Difference

Slang: VOLTAGE

SI unit: volt (V) named after

Alessandro

Giuseppe Antonio Anastasio

Volta

Measured with a voltmeter

Analogous to difference in height, if you want to relate to gravity, or pressure in water pump

By CONVENTION, the positive side of a battery is higher potential.Slide16

Electric Current

What is it?

What are its units?

How do we measure it?

What variables affect how much current exists in an appliance?

Read 2c

Start your word webSlide17

Electric Current

The flow rate of charges

Unit: ampere (amps, or just A)

1 ampere = 1coulomb of charge flowing thru a conductor in 1 second

Measured with an ammeter

By convention, the “current” flows from positive around to negative.Slide18

What Variable Affects what other Variable(s) in a Circuit?

What is the mathematical relationship between the ______________(_____) through a bulb and the ______________(___) across the bulb in an electrical circuit?Slide19

Circuit SchematicsSlide20

What is the mathematical relationship between the current(amps)

thru

one bulb and the potential difference(volts)

across

the bulb?

What is the mathematical relationship between the current(amps)

thru

two bulbs and the potential difference(volts)

across

BOTH bulbs?Slide21

Understanding the Lab

What happened when potential difference was doubled?

How did the results differ when a second bulb was in the loop?

What do the bulbs do to the current? (more bulbs in series means ____ current)Slide22

Ohm’s “Law”: I = D

V/R

The current in a circuit element (like a bulb) is directly proportional to the potential difference across the element, and inversely proportional to the resistance of the elementSlide23

R: Resistance

R =

D

V / I

R =

r

L

/A (

r

=resistivity, L=length, A=cross sectional area)

Note: Important in AP E&M

SI unit: ohm (

W

)

Measured with an ohmmeter

All real conductors have a little of this, insulators have a LOT of it. An ideal conductor has 0

W

and an ideal insulator has ∞

WSlide24

Resistance

What is it? (use The Lazy Mile at the water park)

What happens in the circuit as the resistance changes?Slide25

Example Problem

Ex: A single loop circuit is made with a 1.5 volt battery, and a light bulb. An ammeter is used to measure a 0.15A current in the loop. What is the resistance of the bulb in this circuit?

PCR Current Electricity 3c CYU 1-5, 7,8