Ch 16.2 & 16.3 Current and Circuits Electrical Potential Energy The amount of energy stored between two charges Voltage Is the “push” behind making electrons move Technically, the work it takes to move a charge Measured in Volts (1 J/C)

Voltage Batteries we use in class are 6V, batteries in your calculator are 1.5V This means it would take 6 J to move each Coulomb worth of charge… but each electron is 1.6 x 10-19 C So each Volt can move a lot of electrons

Current When the electrons move it is called current If they flow in one direction, it is called direct current (DC, e.g. battery) If they move back and forth, it is called alternating current (AC, e.g. when you plug something in) https://www.youtube.com/watch?v=JZjMuIHoBeg

Current direct current alternating current Electrons flow in 1 direction alternating current Electrons flow back and forth

Amperage & Resistance A measure of the amount of electrons flowing. Measured in Amps (A) As electrons move, they are slowed down by friction. The amount they are slowed is resistance. Resistance is measured in Ohms (W)

Like Water… So electricity is like flowing water: There’s something pushing the water or some energy source making it flow (push = voltage/volts) You can measure how fast it is flowing (flow = amperage/amps) There are things that slow water down (slowing = resistance/ohms) Conductors have low resistance and allow flow, insulators have high resistance and block flow. Semiconductors kinda allow flow. Superconductors have almost no resistance at very low temps (close to 0K).

Relationships For voltage staying the same: amperage and resistance are indirectly proportional high slowing = low flow For current (amperage) staying the same: voltage must do whatever resistance does or current will decrease If slowing increases, push must increase to keep the same flow

Relationships For resistance staying the same: Examples: voltage must do the same thing as current You need a lot of push to keep a lot of flow Examples: voltage is high and current is low, resistance is… voltage is low and resistance is high, current is… current is high and resistance is low, voltage is… Current is low and voltage is low, resistance is…

Ohm’s Law V=IR R=V/I I=V/R voltage= current x resistance If voltage stays the same, current and resistance are inverses R=V/I resistance = voltage/current If resistance stays the same, voltage and current are proportional I=V/R current= voltage/ resistance If current stays the same, voltage and resistance are proportional

Circuits The actual pathway electrons flow Is like a circle…the electrons have to go all the way around Schematics used to draw:

Series Circuits If there is only 1 way for the electrons to flow, you have a series circuit If the circuit opens (by a switch or something blows out) everything will go dead The lights are equally bright and will dim if you add another (voltage is the same, but resistance has increased so flow will decrease)

Parallel Circuits If there are many pathways for electrons to flow, you have a parallel circuit If the circuit opens (switch or blow out) some things may still have current and work! Adding another light in parallel does not dim the bulbs because you still have the same push, slow and flow for each circuit!

Electrical Safety The amount of Power = voltage x current (P=IV) Too much power = overload = fire! Grounding: providing a third wire to the ground for electrons to flow (third prong of plug) Fuse: metal that melts and opens circuit if too much power Circuit breaker: magnet or strip of 2 metals that acts like a switch and opens