Physics study guide

In a standard circuit with a charging capacitor and a connecting wire is touched for an instant between the capacitor posts, what happens?

The extra wire around the capacitor is bypassing the insulator between the posts, making the capacitor act as an extension of the wire that is already there, which is why there are sparks and the bulbs stay lit (rather then lighting for only a small amount of time).

How do bulbs in parallel affect flow rate?

The more bulbs added in parallel, the faster the flow rate (and the overall decrease in resistance). -bulbs stay the same brightness, but compass deflection through the main wire is increased -splits between the bulbs; less resistance for each bulb; less overall resistance

How do bulbs in series affect flow rate?

The more bulbs added in series, the slower the flow rate. -bulbs get dimmer and compass deflects less with each bulb added in series

How does the resistance of a wire compare to the resistance of oval and/or round bulbs? And based off of that answer, how long does it take to "reset" a capacitor?

The resistance of a wire is much less than that of an oval or round bulb, so it takes barely any time to "reset" a capacitor.

How do wires in series or parallel affect the circuit?

They do not affect anything. -when multiple wires are added, bulb brightness and compass deflection stay the same as they were without the added wires

How can we tell that the battery charges a capacitor?

When a capacitor is placed in a circuit with just bulbs after being in a circuit with a battery pack, the bulbs in that circuit light (even if briefly).

How are Genecons similar to batteries?

When the Genecon's handle is turned, it creates energy that flows through the circuit, like a battery. -deflects the compass the same way as the battery pack -a battery provides energy and makes charge flow through the wires and bulbs -a Genecon also provides energy and also makes the bulbs light

How to measure flow rate with bulbs in parallel

When the bulbs in the circuit are *in parallel*, their flow rates are *added up to* the flow rate through the battery

How to measure flow rate with bulbs in series

When the bulbs in the circuit are *in series*, their flow rates are *the same as* the flow rate through the battery (and the other bulbs)

Given three of the same kind of bulb, how could you combine them to obtain the maximum or the minimum resistance?

You could put them all in series for maximum resistance and in parallel for minimum resistance

If you were given a different type of bulb than round or oval (Brand X), how could you determine how the resistance of the new bulbs compares to that of the round and oval bulbs?

You could test the amount of compass deflection in the wires for each type of bulb in a standard circuit, or you could compare how long each type of bulb stays lit when charging a capacitor

What units are used to measure flow rate/electric current?

amps

Put the combinations in order from longer lighting time to shortest lighting time: a. a single oval bulb b. two oval bulbs in series c. two oval bulbs in parallel d. an oval bulb and a round bulb in series e. an oval bulb and a round bulb in parallel

b, d, a, c, e ( 1) two oval bulbs in series, 2) an oval bulb and a round bulb in series, 3) a single oval bulb, 4) two oval bulbs in parallel, 5) an oval bulb and a round bulb in parallel)

Where is the ammeter in relation to where you want to know the flow rate?

in series

flow rate

measures the number of charge particles that pass a given point in the circuit each second

How are Genecons different than batteries?

-a battery does not involve physical movement to produce energy, but a Genecon does (because you have to turn the handle)

In a standard circuit with two bulbs in parallel and a 3rd bulb is added in parallel with (only) one of the bulbs, does it increase or decrease the *overall* resistance?

It decreases the overall resistance because the flow rate through each bulb is faster than it was before.

How does adding a second 3-cell battery pack affect an already charged capacitor?

It increases the charge-holding capabilities of the capacitor (adds even more charge to it). -bulbs light for less time and are dimmer

How is flow rate determined?

It is determined by the *difference* in the number of cells. -as more cells are added opposite the original 3-cell battery pack, compass deflection decreases (but stays the same direction) for each wire -bulbs get dimmer as more cells are added -the cells start to cancel each other out -bulbs are the same brightness

In a circuit with four round bulbs in series and a capacitor around the entire circuit, how does the capacitor slow down the transient?

It takes more charge to make the pressure change: the volume of the capacitor plates is greater than that of the wires, which slows down the process -there is more volume for the pressure to change in

How does mixing bulbs (oval and round) in series affect flow rate and pressure in each part of the circuit?

Mixing bulbs in series *does not* affect flow rate but *does* affect pressure difference. -we set up a circuit with an oval bulb with a capacitor around it (so the transition goes slower so we can see it) then a round bulb in series -round bulb started very bright then ended not visibly on -oval bulb started medium brightness then ended very bright -compass deflected the same direction and amount under each wire

Does the amount of charge stored in a charged capacitor depend on the type of bulb through which it was charged?

No, the capacitor ends up with the same amount of charge with both types of bulbs. Evidence: -we charged a capacitor through round and oval bulbs and then discharged the capacitor through a Genecon -the handle turned the same amount for both types of bulbs

What is the complete path of a bulb?

One wire touching the tip and one touching the thread, allowing the bulb to light

How to find out if a capacitor is already charged without discharging it

Put a capacitor in a charging circuit - if nothing happens (if the bulbs don't light) then it is charged

What is resistance?

Resistance is defined as volts/amps -units are ohms (Ω)

How to charge a capacitor

Set up a standard circuit with a battery, two bulbs, four wires, and a capacitor between the bulbs

How to discharge a capacitor

Set up a standard circuit with a battery, two bulbs, four wires, and a capacitor between the bulbs. Take out the battery and close the circuit (with the wires)

In a charging circuit with two round bulbs compared to a discharging circuit with one round bulb: T or F: The single bulb shines brighter than either bulb in the two-bulb circuit.

TRUE

In a charging circuit with two round bulbs compared to a discharging circuit with one round bulb: T or F: The total resistance of the two bulbs is greater than that of the single bulb.

TRUE

In a charging circuit with two round bulbs compared to a discharging circuit with one round bulb: T or F: Charge flows at a greater rate through the single bulb than through the two bulbs.

TRUE

True or false: Charge flows in only one direction through the battery pack.

TRUE: When we set up a standard, closed circuit, the compass needle deflected the same direction under each wire, indicating that charge flows in only one direction.

True or false: Light bulbs light up just the same regardless of which direction charge flows through them.

TRUE: When you set up a standard circuit and then switch the battery pack around, it changes the direction of charge flow (since charge flows from positive to negative) but the bulbs are the same brightness in both cases.

Does the ammeter have a very high or a very low resistance?

The ammeter has a very low resistance -does not affect the bulbs' brightness when in series in the circuit

Is the battery a source of constant pressure difference or constant flow rate?

The battery is a source of *constant pressure difference*. -compass deflection shows flow rate and it increases as more bulbs are added in parallel to a circuit

How do oval bulbs affect the charging time of a capacitor?

The capacitor takes longer to charge through the oval bulbs -oval bulbs have a higher resistance than the round bulbs because of their thin filament -takes same amount of time to discharge as the round bulbs; the capacitor always holds the same amount of charge

What determines the direction of charge flow?

The direction of the battery determines the direction of charge flow. We know this because all the wires deflect the compass the same direction and amount. When the battery pack is reversed, the compass deflection is reversed.

In a charging circuit with two round bulbs compared to a discharging circuit with one round bulb: T or F: A compass would show a larger deflection for the charging circuit than for the discharging circuit.

FALSE: A compass would show *a larger deflection for the discharging circuit* than for the charging circuit

True or false: In a standard circuit consisting of a battery and lit bulbs, the battery is the source of charge that's moving through the wires.

FALSE: In a standard circuit with a charging capacitor, both the bulbs on either side of the capacitor light. The capacitor plates are separated by an insulator, meaning that charge cannot flow *through* the capacitor. The bulb on one side of the capacitor not connected to the battery still lights, even though the wire connected to it is not receiving charge from the battery because of the insulator in the capacitor, meaning that the battery *is not* the source of charge.

True or false: Metal substances are generally insulators.

FALSE: The wires and the thread and tip of the bulb are all made of metal. Insulators *prevent* charge flow but when we touched the wires to the thread and tip of the bulb, the bulbs lit, so metal substances are generally conductors, not insulators.

True or false: A compass can be used to determine the *exact* direction that charge flows in a circuit.

FALSE: We know that charge flows in one direction, from positive to negative by placing a compass under the wires in a closed circuit and the compass deflecting all the in the same direction; however, in a circuit with just bulbs and a capacitor, the compass cannot tell us the *exact* direction that charge is flowing.

Where does mobile charge originate?

From all the conductors in the circuit. -when compass is placed under each wire, the needle deflects -indicates that charge must come from battery, wires, capacitor, etc.

What is the relationship between pressure difference and flow rate?

In the graph of the two (with current on the x-axis and potential difference on the y-axis) the slope of the graph is the resistance of the object you measured -ΔV=R • I, where -ΔV is the potential difference -R is the resistance -I is the flow rate or current