Need to KnowCASTLE

Section 1

• All bulbs come on at the SAME time.• A CIRCUIT is an unbroken loop of conducting

electrical components that forms a continuous conducting path.

• In order for a bulb to light circuit must connect from positive end of battery to negative.

• CONDUCTOR – permit charges to flow (most metals)

• INSULATOR – prevents charges from flowing

• Conventional charge flow is POSITIVE to NEGATIVE.

• The energy source determines the direction of flow of charge in a circuit (from high pressure terminal to low)

• Be able to draw the path of charge flow in a circuit (positive to negative) and through the bulb – determining if the bulb will light or not.

Section 2

• WIRE has least resistance, then ROUND BULB, then LONG BULB (thickest to thinnest wire).

• FLOW RATE is not the same idea as speed. Flow rate refers to the net charge per second passing through part of a circuit.

• As bulbs are added to a circuit the overall brightness of the bulb goes down (but within that circuit they are the same level of brightness) – see 2.2– Be able to draw STARBURSTS and ARROWTAILS!!!

• Long bulb filament is thinner (like when blowing through the coffee stirrer) therefore it is more difficult for charge to flow so it has a great resistance and highest pressure difference.

• Round bulb filament is thicker (like how it was easier blowing through the regular straw – or a paper towel roll) there making it easier for charge to flow so less resistance and lowest pressure difference.

• Remember – in circuit long bulb was much brighter.

• Wire had least resistance because when testing with a coil of wire (2.8) the compass deflection did not change. Also, when tapping the around the socket on the second bulb that bulb went out b/c charge will travel the path of least resistance (2.9).

• It takes longer to blow through straws taped in a row (series circuit) versus when grouped together (parallel circuit).

• In SERIES both light bulbs lit up and were same brightness.

• In PARALLEL (adding the branch) the first bulb is very bright then the two in a branch are less bright but the same level of brightness.

• Adding resistors in PARALLEL– makes flow easier so less overall resistance.

• Adding resistors in SERIES – makes flow harder so more overall resistance.

Section 3

• Know how to draw a schematic diagram using appropriate symbols.

• That a capacitor consists of two conducting plates separated by an insulating plate, giving it the ability to store charge.

• Charge leaves the bottom plate during capacitor CHARGING. Evidence - compass

• Charge leaves the top plate during capacitor DISCHARGING. Evidence - compass

• A larger capacitor stores more charge – bulbs light longer and are brighter.

• The same amount of charge flows during capacitor CHARGING and DISCHARGING.

• The total resistance of two bulbs is greater than that of a single bulb.

• A compass would show a larger needle deflection for a brighter bulb because it would have a greater flow of charge.

• The GENECON causes charge that’s always present in the wires to move – like a pump causes water in plumbing pipes to move.– Battery does the same

• Exhaling into air capacitor is like CHARGING an electrical capacitor.– The air exhaled into the air capacitor, filling the balloon,

creates pressure in the second chamber forcing air out. Much like in the electrical capacitor – electrical pressure forces charge to leave the bottom plate.

• Inhaling (pulling air back through the air capacitor) is like DISCHARGING an electrical capacitor.

• (+) represents a more-than-normal amount of charge (‘extra’ charge)

• (-) represents a less-than-normal amount of charge (‘missing’ charge)

• 3.13 (along with 2.8 and 2.9) are further proof that wires have very little resistance.

• The internal resistance of a battery increases as batteries run down.– Evidence is that when charging a capacitor the bulbs

dimly light and very brief. When discharging the capacitor and those batteries are removed they light up a little brighter and longer (b/c w/out the battery in the circuit there is less resistance)

Section 4

• As the capacitor is being “charged” the energy in the capacitor approaches same energy as the battery. Closer it gets the less able the battery is able to pump more charge into the plate, making bulbs start to dim.

• When battery is removed, compression in the upper (+) plate will push charge in the reverse direction, discharging the capacitor. Decompression will weaken reverse pushing and make bulbs start to dim.

• Air pressure is the name given to the effort to expand by compressed air.

• Electric pressure is the same effort exerted by compressed air.

• Electric pressure measured in unit called VOLT.• Charge always tries to move from HIGHER

electric pressure to LOWER electric pressure.

• See 4.9 for color-coding circuits.– Red: highest above normal – Orange: above normal– Yellow: normal– Green: below normal– Blue: lowest below normal

– Red always leaves (+) end of battery, Blue always enters (–) end of battery.

– In order for a bulb to light it must have a pressure difference (from high to low)

– The largest difference in pressure (like a red to blue) creates the brightest bulb

– Capacitor charging starts at normal pressure, once charge top wires are highest pressure (red) b/c charge accumulated on top plate while bottom wires are lowest pressure (blue) b/c charge left bottom plate.

– Opposite happens in capacitor discharging b/c charge leaves top plate and travels back to bottom plate.

Section 5

• A parallel pair of bulbs has less resistance than a single bulb.

• Parallel resistors provide more paths from a HIGH to LOW pressure region. So a given pressure difference will drive a greater net flow rate from HIGH pressure to LOW pressure than it does in a single path.

• So…– “Less resistance” lets the same pressure diff drive a

greater flow rate.– “Less resistance” lets the same flow rate be driven by

less pressure diff.

• Branching in parallel circuits lowers resistance: