Parallel Circuits Grade 8
polarity in a parallel circuit
- to +
electrical circuit
...a closed or complete path in which an electric current flows
What are some differences between parallel and series circuits?
1- In a parallel circuit, only voltage stays constant, but in a series circuit, only current stays constant. 2-In a parallel circuit, when one bulb goes out, the rest will still be lit, but in a series circuit, they will all go out. 3-In a parallel circuit, you add up the reciprocals of the resistance, but in a series circuit, you simply add them up.
does not interrupt
A break in any one path in a parallel circuit _______ the flow of electric charge in other paths.
series circuit
A circuit that contains only one path for current flow.
Circuit
A complete path for electrons to flow
omhs law for parallel circuits
resistance decreases, current increases
fuse
A device that breaks to protect against excessive current. Must be replaced.
Kirchhoff's current law
A law stating that the total current into a node equals the total current out of a node. Equivalently, it can be stated that the algebraic sum of all the currents entering and leaving a node is zero.
Current divider
A parallel circuit in which the currents divide inversely proportional to the parallel branch resistance.
Node
A point or junction in a circuit at which two or more components are connected.
How do you work out the current?
A1 = A2 + A3 A1 = A4
To increase the current in a parallel circuit . . .
Add another branch
parallel circuit
An electric circuit with two or more paths through which charge can flow
power
An independent path in a parable circuit
branch
An independent path in a parallel circuit
You add up what in a parallel circuit?
Current.
Resistance will . . . when the temperature decreases
Decrease- the flow of electrons are less rapid, therefore they flow easier
REQ
EQUIVALENT RESISTANCE
What is an advantage of a parallel circuit?
Equal voltage/potential difference to each portion of the circuit.
1/Rt= 1/R1+1/R2+1/R3
Formula to figure out the total resistance in a parallel circuit.
I1+I2+I3=It
How can you find the current in a parallel circuit. Formula
Calculating current in parallel circuits
I = V/R; calculate for each branch
parallel circuits
In _________ there are multiple paths for current.
current
In parallel circuits the _______ in each device does not have to be the same.
voltage
In parallel circuits the _________ across each device does not have to be the same.
What happeneds to the current in a parallel circuit?
It is shared between each branch.
What happens to the potential difference?
It is the same of each component.
SUM
MEANS ADD
PRODUCT
MEANS MULTIPLY
Parallel Circuit
Multiple paths for electrons to flow.
After going through resistors, does current change?
No! Current does not change after going through resistors.
RECIPROCAL
ONE DIVIDED BY
Branch
One current path in a parallel circuit.
laws of a parallel circuit
P=p1+p2+p3... I=i1+i2+i3... R=1/r1+1/t2+1/r3... E=e1=e2=e3...
IT = IR1 + IR2 + IR3
PARALLEL CURRENT
RT = R/N
PARALLEL RT EQUAL RS
VT = VR1 = VR2= VR3
PARALLEL VOLTAGE
NODE
PLACE WHERE CURRENT SPLITS
Current flows from . . .
Positive to negative
Circuit breaker
Protects against high current, but can be reset.
How do you work out the resistance?
R1 < smallest out of R2 & R3
PRODUCT OVER SUM
RT FOR PARALLEL TWO RESISTOR
50
RT OF 2 100'S IN PARALLEL
25
RT OF 4 100'S IN PARALLEL
The electrons only split when there's a ______________.
Resistor on that branch.
What is a disadvantage of a parallel circuit?
Source is needed to supply current.
KIRCHOFF
TOTAL CIRCUIT LAWS
Parallel
The relationship between two circuit components that exists when they are conneted between the same pair of nodes.
What happens to the resistance?
The resistance at the cell is always smaller than the smallest resistance.
Divides among the branches
The total current in circuits does what in a parallel circuit
Sum of current in the parallel branches
The total current is equal to,
Current
This is divided among the branches of the parallel circuit and all of the current in each branch added up equals the total amount of current in the circuit.
Resistance
This is the amount of resistance in a parallel circuit, it is found by using the recipricals of the resistances and adding them up.
Voltage
This is the drop over each resistor and it is the same as the gain over the bulb in each branch of the parallel circuit
What is another way to find the total resistance besides adding up the reciprocals?
Total voltage/Total current= Total resistance
True
True or False? If there is a break in a parallel circuit, electricity will still flow through the other parts of the circuit.
Common uses
Used to wire homes and businesses
How do you work out the potential difference?
V1 = V2 = V3
Electric potential is also known as . . .
Voltage and potential difference
What stays constant in a parallel circuit?
Voltage/Potential Difference
V1 + V2 + V3= Vt
What is the formula for voltage, or potential difference in a parallel circuit.
junction
Where branches joint or split
wire
Where most of the electrons in a circuit come from
In a parallel circuit, what do you do to the resistance?
You put it into the reciprocal. (1/Rt=1/R1+1/R2+1/R3)
How would you find the current in each branch if the voltage was 12V and the resistors had 3 ohm's?
You would divide the voltage by the amount of ohm's in the resistors. So the answer would be 4 amps. (12/3=4)
A parallel circuit composed of a 120 ohms and a 220 ohms resistor has a supply voltage of 240 V. What is the total circuit current?
a. 3.091 A
A parallel circuit composed of a 10 ohms and a 22 ohms resistor. It has a supply voltage of 60 V. What is the current in the 10 ohms resistor?
a. 6 A
A three-branch parallel circuit has resistances of 22 k ohms, 68 k ohms, and 33 k ohms connected to a 300 V source. What is the total power of the circuit?
a. 8.14 W
Current is measured in...
amps
A parallel circuit composed of a 150 ohms and 270 ohms resistor has a supply voltage of 120 V. What is the current in the 150 ohms resistor?
b. 0.8 A
A two-branch parallel circuit has a 30 Ohms and a 15 ohms resistor. What is the total resistance?
b. 10 ohms
A three-branch parallel circuit has a total resistance of 385.83 Ohms. Two of the resistors are 680 ohms and 1500 ohms. What is the value of the third resistor?
b. 2200 ohms
In parallel circuit, the amount of current flow in a branch is known as the ________ of the branch.
b. load
In a parallel circuit, the total resistance is_______ value resistance.
b. smaller than the smallest
A 62- k ohms and an 82- k ohms resistor has a supply voltage of 480 V. What is the power of the 82- k ohms resistor?
c. 2.81 W
Current in parallel circuits
changes as power is used
Break in parallel circuit
creates an open circuit in only one branch of circuit; current still flows along other branches
kirchoffs current law
current in =current out
A parallel circuit a composed of two 60 ohms resistors. what is the total resistance?
d. 30 ohms
When you decrease the number of resistors in a parallel, total resistance . . . and current . . .
decreases, increases
As branches increase, resistance ____________.
decreases.
Voltage drop
does not exist; voltage is constant
parallel
electric devices connected in __________________ are connected to the same two points of an electric circuit
Total current in parallel circuit
found by adding current in each branch of circuit
Adding another branch will
increase current
As branches increase, current _____________.
increases.
Voltage in parallel circuit
is constant
In a series circuit, the current...
is the same throughout
Current wants to travel in the path of . . .
least resistors
Parallel circuits
multiple paths (branches) for current to flow
equals the total current
n parallel circuits, the sum of the currents in all f the devices ________.
Resistance is measured in...
ohms
voltage effects in parallel circuits
power is connected in series to increase voltage output power is connected in parallel to increase current
The current in the battery is . . .
the sum of current in the branches
Voltage is measured in...
volts
