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Define circuit diagram
Draw the circuit diagram representations of the following:
- Circuit diagram: a logical picture of what is connected to what. The actual circuit may look different from the circuit diagram, but have the same logic and connections.
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Draw the circuit diagram for the simple circuit shown and label the emf, R, and C of the capacitor. Also state the direction of the current
The wires, which in practice may bend and curve, are shown as ______ _______ connections between the circuit elements
 - Current goes in a clockwise direction starting from the battery's positive terminal and ending on its negative terminal
- straight-line connections
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B. Its not connected to the negative end so its not a closed/complete circuit
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Explain the Junction Rule
It is a statement of conservation of ______ and ______
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Explain the Loop Rule
ΔVi is the potential difference of the ___ ______ of the loop.
It is a statement of conservation of _____
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The potential energy ______ whenever the charge moves through the potential drop.
ΔV R for a resistor is always ________ (why?)
Why do we often speak of the "voltage drop" across the resistor?
ΔV bat can be negative for a battery (why?)
In each diagram, ΔV = ______ and the circuit element is ______ from a to b, left to right
- decreases
- ΔVR for a resistor is always negative because the potential in a resistor decreases along the direction of the current
- Because the potential across a resistor always decreases
- ΔVbat can be negative for a battery because the current can go through a battery in a "wrong," positive-to-negative direction when it is forced to do so by other, higher voltage batteries.
- ΔV = Vb - Va
- traversed
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The potential energy _______ whenever the charge passes through a battery from the negative terminal to the positive terminal
ΔVR for a resistor increases (How is this possible?)
**pg 776
- increases
- ΔVR for a resistor is positive because the potential in a resistor increases along the direction opposite the current
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Since the potential drop in an ideal wire is ______, state the formula for:
ΔVloop (4)
ε (1)
- zero
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B. junction rule: 2.5 - 1.5 = 1.0 A
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- A. The signs for both batteries are the same and both batteries are in series, so we can combine them into one battery of ε = 7.5 V
- Because all the resistors are in series ☞Kirchhoff's Law: Loop Rule
- ΔVloop = ΔVbat + ΔVR1 + ΔVR2 + ΔVR3 = 0
- ΔVloop = ε + ΔVR1 ΔVR2 + ΔVR3 = 0
- (7.5 V) + (-3.0 V) + (-ΔVR2) +(-2.5 V) = 0
- 2.0 V = ΔVR2
**Note: If the symbols for the batteries were opposite it would be 4.5 V - 3.5 V = 1.5 V and the 4.5 V battery would still be the dominant battery, so it would still dictate the direction of the current
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- E. The dominant battery (9 V) dictates the direction of the current which will be clockwise. However, that current passes through the 6 V battery from + to - instead of - to +, so the current it will be a voltage drop: 9 V - 6 V = 3 V
- OHM's Law:
- I = ΔV/R
- I = (3.0 V)/(3 Ω) = 1 A
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- Low to high so
- ε - IR1 - IR2 = 0
- ε = +12V and IR1 = I(12) and IR2 = I(6)
- 12 - 18I = 0
- I = 18/12 = 2/3
- So D.
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A circuit with multiple elements can have different ways of connecting them.
Two basic ways of connection (name and draw them)
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When two or more elements are connected end-to-end, they are said to be in a ______ _______. There is NO _______ in between. Each element receives the same amount of _______ passing through it, but with different _______ across.
- series combination
- junction
- current
- potential
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Same current pass through each resistors
Applying Kirchhoff's loop law:
___ - ___ - ___ = 0
ε = ___ + ___
We can replace two resistors with a single resistor having the value Req = R1 + R2
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The potential difference across the battery is also applied to the ________ ________ (___):
ε = _____
The equivalent resistance has the same effect on the circuit as the ______ _______ (why?)
- equivalent resistance (Req):
- ε = IReq
- series combination
- because it results in the same current (I) in the battery
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The equivalent resistance of three or more resistors connected in series is:
Req = ?
The equivalent resistance of a series combination of resistors is the numerical sum of the _______ _________
It is always ________ than any individual resistance
- Req = R1 + R2 +R3 +...
- individual resistances
- greater
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In a circuit with one bulb, a battery drives the current IA = ____ through the bulb A.
In a circuit with two bulbs in series with the same resistance R, the equivalent resistance is Req = ___
The current running through the bulbs is:
IB = ____ = ____
Since the emf is the same for both circuits,
IB = ____
Thus, bulb B & bulb C are _____ bright, but they are ______ than bulb A because there is _____ current
- IA = ε/R
- Req = 2R
- IB = IC = ε/2R
- IB = 1/2(IA)
- equally bright
- dimmer
- less
 - **Note: Bulbs of the same complete circuit are of the same current and hence brightness. All things equal, A should be brighter than B and C
- The Christmas bulbs are not in series, maybe every 3 or 4 bulbs are but not all of them
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A battery is a source of ______ ______, not a source of _______.
The battery does provide the current in a circuit, but the amount of current depends on the _______.
The amount of current depends jointly on the ________ ______ and the ________ of the circuit attached to the battery
- potential difference
- current
- resistance
- battery's emf and resistance
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Consider two resistor in a parallel combination:
Both resistors are connected directly across the terminals of the battery
The potential difference across the resistors are ____ _____:
ΔV = ____ = ____
ΔV is the ______ ______ of the battery
- the same
- ΔV = ΔV1 = ΔV2
- terminal voltage
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When charges reach a junction, the current splits into two parts, with some going toward R1 and the rest going toward R2
Define Junction
- Junction: any such point in a circuit where a current can split
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This split results in _____ current in each individual resistor than the current leaving the battery. The current (I) that enters point a must equal the total leaving that point:
I = ______ = ______ = _______
I1 is the current in R1 and I2 is the current in R2
- less
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The current in the equivalent resistance Req is:
I = ___ = ___
The equivalent resistance has the _____ _____ on the circuit as the two resistors in parallel
The equivalent resistance draws the same ______ from the battery
- I = ΔV/Req = ε/Req
- same effect
- current (I)
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The equivalent resistance of 3 or more resistors in parallel is given by:
1/Req = ?
The inverse of the equivalent resistance of two or more resistors in a parallel combination is equal to the sum of the _______ of the individual resistances.
The equivalent resistance is always ______ than the smallest resistance in the group
Parallel resistors provide more _______ for charge to get through
An analogy is driving in heavy traffic (explain).
 - inverses
- less
- pathways
- If there is an alternate route for cars (current) to travel, more cars (current) will be able to flow freely
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