Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are...
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![Page 1: Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are added? –The resistance will increase (light bulbs are.](https://reader036.fdocuments.us/reader036/viewer/2022062511/551bde1c550346be588b5c52/html5/thumbnails/1.jpg)
Circuits and Power
![Page 2: Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are added? –The resistance will increase (light bulbs are.](https://reader036.fdocuments.us/reader036/viewer/2022062511/551bde1c550346be588b5c52/html5/thumbnails/2.jpg)
Series 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 = ↓ Ihttp://iss.cet.edu/electricity/
![Page 3: Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are added? –The resistance will increase (light bulbs are.](https://reader036.fdocuments.us/reader036/viewer/2022062511/551bde1c550346be588b5c52/html5/thumbnails/3.jpg)
Drawing a Series Circuit
www.bbc.co.uk
![Page 4: Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are added? –The resistance will increase (light bulbs are.](https://reader036.fdocuments.us/reader036/viewer/2022062511/551bde1c550346be588b5c52/html5/thumbnails/4.jpg)
Series 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
![Page 5: Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are added? –The resistance will increase (light bulbs are.](https://reader036.fdocuments.us/reader036/viewer/2022062511/551bde1c550346be588b5c52/html5/thumbnails/5.jpg)
Parallel 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/
![Page 6: Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are added? –The resistance will increase (light bulbs are.](https://reader036.fdocuments.us/reader036/viewer/2022062511/551bde1c550346be588b5c52/html5/thumbnails/6.jpg)
Drawing 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
![Page 7: Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are added? –The resistance will increase (light bulbs are.](https://reader036.fdocuments.us/reader036/viewer/2022062511/551bde1c550346be588b5c52/html5/thumbnails/7.jpg)
Parallel 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
![Page 8: Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are added? –The resistance will increase (light bulbs are.](https://reader036.fdocuments.us/reader036/viewer/2022062511/551bde1c550346be588b5c52/html5/thumbnails/8.jpg)
Decorative 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
![Page 9: Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are added? –The resistance will increase (light bulbs are.](https://reader036.fdocuments.us/reader036/viewer/2022062511/551bde1c550346be588b5c52/html5/thumbnails/9.jpg)
Series and Parallel Combo
Are all the bulbs the same brightness? Why?
Which light bulb can you unscrew to have 1 bulb lit… 2 bulbs lit?
A B
C
![Page 10: Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are added? –The resistance will increase (light bulbs are.](https://reader036.fdocuments.us/reader036/viewer/2022062511/551bde1c550346be588b5c52/html5/thumbnails/10.jpg)
Series and Parallel Combo
Which bulb would be the brightest? Why?
B
A C
Which light bulb can you unscrew to have 1 bulb lit… 2 bulbs lit?
![Page 11: Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are added? –The resistance will increase (light bulbs are.](https://reader036.fdocuments.us/reader036/viewer/2022062511/551bde1c550346be588b5c52/html5/thumbnails/11.jpg)
More Series/Parallel Circuits
Which bulb would be the brightest? Why?
C
B
A
Which light bulb can you unscrew to have 2 bulbs lit… 0 bulbs lit?
![Page 12: Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are added? –The resistance will increase (light bulbs are.](https://reader036.fdocuments.us/reader036/viewer/2022062511/551bde1c550346be588b5c52/html5/thumbnails/12.jpg)
Ohm’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
![Page 13: Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are added? –The resistance will increase (light bulbs are.](https://reader036.fdocuments.us/reader036/viewer/2022062511/551bde1c550346be588b5c52/html5/thumbnails/13.jpg)
Relationships
• As Resistance goes up, current goes down
• As voltage goes up, current goes up
![Page 14: Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are added? –The resistance will increase (light bulbs are.](https://reader036.fdocuments.us/reader036/viewer/2022062511/551bde1c550346be588b5c52/html5/thumbnails/14.jpg)
Formula
• V = IR
• Voltage = current x resistance
V = IR
I = V÷R
R = V÷I
V
I R
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Power
• 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
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Power
• 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 CurrentP = VIUnit = Watt
![Page 17: Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are added? –The resistance will increase (light bulbs are.](https://reader036.fdocuments.us/reader036/viewer/2022062511/551bde1c550346be588b5c52/html5/thumbnails/17.jpg)
Formula
• P = VI
• Power = Voltage x Current
P = VI
V = P÷I
I = P÷V
P
V I
![Page 18: Circuits and Power. Series Circuit What happens to the resistance of the circuit as more bulbs are added? –The resistance will increase (light bulbs are.](https://reader036.fdocuments.us/reader036/viewer/2022062511/551bde1c550346be588b5c52/html5/thumbnails/18.jpg)
Do Just Light Bulbs have a Wattage?
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/
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Electric 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)
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