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Voltage
Voltage
● Voltage is the measure of the electrical energy
● It is the energy that causes electrons to want to go from
one place to another
Picture
Source:http://www.preparednesspro.com/time-to-stock-up-on-toilet-paper-batterie
s-and-more-cheap
Picture source:https://en.wikipedia.org/wiki/Waterfall
Voltage
● Voltage is measured in Volts (V)
● What happens if a battery provides 0 volts?
● The higher the voltage, the _________ (more/less) the
electrons want to leave the battery.
Current
Current
● Current is the flow of electrons. It is the speed of the
electrons.
● Current is measured in Amperes (Amps, A).
● 1 Ampere = 6.24 quintillion electrons travelling through a
single point per second.
AC/DC
There are actually two types of current!
Direct Current (DC) is when electrons travel in one direction.
Alternating Current (AC) is when the electrons occasionally change directions.
Think about it
1) What happens when the current is 0 Amps?
2) One circuit has a current of 2 Amps. Another circuit has a
current of 3 Amps. In which circuit is the current moving
faster?
3) If we increase the voltage, will current increase or
decrease?
Resistors
Review from last week
● Can anyone describe what voltage is?
● Can anyone explain what current is?
● Circuit A has a current of 2 amperes, and circuit B has a
current of 4 amperes. In which circuit are the electrons
traveling faster?
● If we increase the voltage, will current decrease or
increase?
Too much energy!
●
●
Electrical current is similar to water flowing
Imagine you wanted to provide water to your faucet directly from the Niagara
Falls! What would happen?
Picture source: http://www.niagarafallslive.com/Facts_about_Niagara_Falls.htm
Picture Source :
http://www.americanstandard-us.com/kitchen-produ
cts/kitchen-faucets/
Too much energy!
● Scenario: Imagine you had a lightbulb that
would break if the voltage went above 1.0 V.
You only have a 1.5 V battery.
● What would you do to lower the voltage?
Resistors
Answer: Resistors!
●
●
A resistor resists current
Some of the energy from the battery is ‘wasted’ on the resistors
Resistors
●
●
All the components in a circuit provides resistance
○ Wires provide almost no resistance
Resistance is measured in Ohms
Ohms Symbol
https://en.wiktionary.org/wiki/%CE%A9
Circuit Symbol
Questions
Think it out…
●
●
●
If we decrease the resistance in a circuit, will current increase or decrease?
Why?
○ Current will increase.
If we increase the resistance in a circuit, will the light bulb shine brighter or
dimmer? Why?
○ The light bulb will be dimmer.
What happens when a component has infinite resistance?
○ There is no current.
Special Snap Circuit Pieces
Photoresistor
●
●
Has infinite resistance in the dark
Has a resistance of around
1000 Ω in bright light
Adjustable Resistor
●
You can vary the resistance
Reminder...
Snap Circuit LEDs always need to have a resistor.