bellwork draw a circuit diagram that has one battery and two light bulbs
TRANSCRIPT
Bellwork
Draw a circuit diagram that has one battery and two light bulbs.
Bellwork
1) If I remove a light bulb from the below circuit, then what happens to the other light bulbs?
2) If I remove a light bulb from the below circuit, then what happens to the other light bulbs?
Two Types of Electric Circuits
• Series
• Parallel
Series Circuits
•Provide a single path through the circuit
If one bulb is removed all light bulbs turn off
Parallel CircuitsEach device connects to the voltage source
If one bulb is removed others will remain on
Noticing the difference
• Series or parallel?
SeriesParallel
Series or Parallel?• Ask yourself: Does the circuit provide more
than one path for the current?
Yes = Parallel
NO = Series
Series or Parallel?
Parallel
Series
Once More!
Series Parallel
BellworkLabel the circuit diagrams below as either parallel or series.
Current and Potential Difference across Series Circuits
IT = I1 = I2 = I3 = ….
VT = V1 + V2 + V3 + ….
IT
VT
I2
V2
I3 V3
I1 V1
Current and potential difference across Parallel Circuits
IT = I1 + I2
VT = V1 = V2
IT
VT
I2
V2
I1
V1
1st - Interpret correctly
V
A
V
A
V
V
V
A
Typical Problem
• If each Volt meter measures a potential difference of 10 V what is the potential difference at the battery?
V2
V1
V3
In this series circuit, if ammeter 1 shows a current of 1.0 amperes, what
will be the reading of ammeter 2?
A2A1 I2I1
In this circuit, if voltmeters 1 and 2 both show measurements of 1.5
volts, what will be the reading of the voltmeter VT?
V2V1
VT
In this parallel circuit, if ammeters 1 and 2 both show measurements of 0.5 amperes, what will be the current IT measured by ammeter
AT?
A1
AT
A2
I2
I1
IT
Series Circuit
Req = R1 + R2 + R3 + ….
R1
R2
R3
Req
Equivalent Resistance
The total amount of resistance of a complete circuit
Example
• What is the equivalent resistance of this circuit?
R1 = 15 ohm
R2 = 10 ohm
R3 = 5 ohm
Req = ?
Example
• Find the resistance in R2?
R1 = 20 ohm
R2 = ? ohm
R3 = 5 ohm
Req = 45 ohm
Example:
• A student needs a 10 ohm resistor to complete a circuit, but only 2 ohm resistors are available. Which of the following should be done to complete the circuit?
a. Connect five 2 ohm resistors in parallel
b. Connect five 2 ohm resistors in series
c. Connect three 2 ohm resistors in series and two 2 ohm resistors in parallel
d. Connect two 2 ohm resistors in series and three 2 ohm resistors in parallel
Example
• A student needs a 20 ohm resistor to complete a circuit, but only 2 ohm resistors are available. What should be done to complete the circuit?
Parallel Circuit
R1Req R3R2
...1111
321 RRRReq
• Find the equivalent resistance
R1 = 20ΩReqR3 = 20 ΩR2 = 20 Ω
• Find the equivalent resistance
R1 = 20ΩReqR3 = 5 ΩR2 = 10 Ω
• Find the equivalent resistance
R1 = 30 ΩReqR3 = 10 ΩR2 = 15 Ω
Law of Conservation of current
• At any junction in a circuit the sum of the currents entering the circuit must equal the sum of the currents leaving the circuit
P
7A
3A
4A
Toward point P
Away from point P
Typical Question
• The diagram below represents currents in branches of a circuit. What should be the reading in ammeter A?
P6A
5A
A
Example 2
• The diagram below represents currents in branches of a circuit. What should be the reading in ammeter A?
P 2A
6A
A
5A
Example 3• Which diagram represents the correct current
direction in a segment of an electric circuit
4 A
2 A
2 A
a) 4 A
2 A
2 A
b)
4 A
2 A
2 A
c) 4 A
2 A
2 A
d)
One More!
• What is the reading in ammeter A
A
4 A 3 A
5 A