# Understanding Circuit Resistance and Power Series Circuits

In this topic, we explore the concept of circuit resistance and power series circuits. When more bulbs are added to a circuit, the resistance in the circuit will increase since the bulbs serve as

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## About Understanding Circuit Resistance and Power Series Circuits

PowerPoint presentation about 'Understanding Circuit Resistance and Power Series Circuits'. This presentation describes the topic on In this topic, we explore the concept of circuit resistance and power series circuits. When more bulbs are added to a circuit, the resistance in the circuit will increase since the bulbs serve as. The key topics included in this slideshow are . Download this presentation absolutely free.

## Presentation Transcript

Slide1Circuits and Power

Slide2Series Circuit• What happens to the resistance of the circuit as more bulbs are added? – The resistance will increase (light bulbs are resistors) • How do you know? – The bulbs are not as bright …  ↑   R = ↓ I http://iss.cet.edu/electricity/

Slide3Drawing a Series Circuitwww.bbc.co.uk

Slide4Series Circuit & Broken Bulbs• Why do all the lights turn off when one is unscrewed? – The path is broken – the current needs to go through each light bulb in order to flow ( there is only 1 path for the current to take ) www.bbc.co.uk

Slide5Parallel Circuit• What happens to the resistance of the circuit as more “branches” are added? – The resistance decreases – there are  several paths for the current to follow  ( think about the difference in the flow of water out of a bucket with 1 hole in it verses several holes ) • How do you know? – The bulbs are bright  …  ↓R = ↑I http://iss.cet.edu/electricity/

Slide6Drawing a Parallel Circuit• There are different “branches” of the circuit • Each bulb is connected to the battery by a separate path www.bbc.co.uk

Slide7Parallel Circuits and Broken Bulbs• Why does one bulb stay lit when the other is unscrewed? – The current from the battery “splits” up to go through the different branches – The path to the other bulb is not broken – the current can take another path www.bbc.co.uk

Slide8Decorative Strings of Lights• Which type of circuit would you want your decorative strings of light to have? – Parallel • Why? – So the whole string does not go out when one bulb breaks

Slide9Series and Parallel ComboAre all the bulbs the same brightness?  Why? Which light bulb can you unscrew to have 1 bulb lit… 2 bulbs lit? A B C

Slide10Series and Parallel ComboWhich bulb would be the brightest?  Why? B A C Which light bulb can you unscrew to have 1 bulb lit… 2 bulbs lit?

Slide11More Series/Parallel CircuitsWhich bulb would be the brightest?  Why? C B A Which light bulb can you unscrew to have 2 bulbs lit… 0 bulbs lit?

Slide12Ohm’s Law• Current – the flow of electrical charge » Unit: Amp » Abbreviation: I • Resistance – the measurement of how hard it is for current to flow » Unit: Ohm » Abbreviation: R • Voltage – the “force” that causes current to flow » Unit: Volt » Abbreviation: V

Slide13Relationships• As Resistance goes up, current goes down • As voltage goes up, current goes up

Slide14Formula• V = IR • Voltage = current x resistance                                            V = IR                                            I = V ÷ R                                            R = V ÷ I   V I R

Slide15Power• Power = The rate at which energy is transformed from one form to another – electrical energy to thermal energy – electrical energy to mechanical energy – electrical energy to light energy

Slide16Power• Potential Energy for a circuit?  Voltage • Rate of flow of energy?  Current (remember this means # charges flowing past a point per second) • So what does power equal?  Power = Voltage x Current  P = VI  Unit = Watt

Slide17Formula• P = VI • Power = Voltage x Current                                            P = VI                                            V = P ÷ I                                             I = P ÷ V P V I

Slide18Do Just Light Bulbs have aWattage? Typical Wattages of Various Appliances • Here are some examples of the range of nameplate wattages for various household appliances: • Aquarium = 50–1210 Watts • Clock radio = 10 • Coffee maker = 900–1200 • Clothes washer = 350–500 • Clothes dryer = 1800–5000 • Dishwasher = 1200–2400 (using the drying feature greatly increases energy consumption) • Dehumidifier = 785 • Fans – Ceiling = 65–175 – Window = 55–250 – Furnace = 750 – Whole house = 240–750 • Hair dryer = 1200–1875 • Heater  (portable)  = 750–1500 • Clothes iron = 1000–1800 • Microwave oven = 750–1100 • Personal computer – CPU - awake / asleep = 120 / 30 or less – Monitor - awake / asleep = 150 / 30 or less – Laptop = 50 • Radio  (stereo)  = 70–400 • Refrigerator  (frost-free, 16 cubic feet)  = 725 • Televisions (color) = 65 – 170 • Toaster = 800–1400 • Toaster oven = 1225 • VCR/DVD = 17–21 / 20–25 • Vacuum cleaner = 1000–1440 • Water heater  (40 gallon)  = 4500–5500 http://www.eere.energy.gov/

Slide19Electric Bills - FYI• The cost of electricity is based on: – Power use of the building (kW) – Amount of time power was used (hr) – Power x Time = Energy use (kWh) • The power company then multiplies your energy use by a generation rate (and adds various fees as well)