parallel circuits – chapter 5 a parallel circuit provides more than one current path between any...
Post on 20-Jan-2016
224 Views
Preview:
TRANSCRIPT
Parallel Circuits – Chapter 5
• A parallel circuit provides more than one current path between any two points.
• Each current path in a parallel circuit is referred to as a branch.
Two Branches Three Branches
How many branches?
Parallel Circuit Characteristics
Voltage and Current Values
Voltage is the same across all components
(a) No parallel branches (b) V1 = V2 = VS
Parallel Circuit Characteristics
Current Characteristics Source current is the sum of all branch currents
nT IIII ...21
whereIn = the current through the nth branch in
the circuit
The total current in the circuit is IT = I1 + I2 + I3
IT = 5mA + 10mA + 20mA = 35mA
Parallel Circuit Characteristics
Voltage and Current Values Current through each branch is determined by the source voltage
and the resistance of the branch.
Sbranch
branch
VI
R
TEAM ACTIVITY
Use Ohm’s law to calculate the resistance in each branch.
TEAM ACTIVITY
1
102000
0 005R
.
2
101000
0 010R
.
3
10500
0 020R
.
TEAM ACTIVITY
Use Ohm’s law to calculate the total resistance.
TEAM ACTIVITY
10285 71
0 035TR ..
TEAM ACTIVITY
1
102000
0 005R
.
2
101000
0 010R
.
3
10500
0 020R
.
10285 71
0 035TR ..
Calculate1 2 3
1 1 1
R R R
1
TR
Summary
1 2 3
1 1 1 1
TR R R R
1 2 3 TI I I I
1 2 3 SV V V V
1 2 3
11 1 1 TR
R R R
Common Mistake
1 2 3
1 1 1 1
TR R R R 1 2 3 T
Series Circuit
R R R R
TEAM ACTIVITY
1P
2P
3P
TP
TEAM ACTIVITY
1 0 05P . W
2 0 1P . W3 0 2P . W
0 35TP . W
1 2 3TP P P P
Special Case – Equal Resistances
• When any number of equal resistances are connected in parallel, the total resistance is equal to the value of one resistor divided by the number of branches
Shorthand notation for parallel
Special Case – Equal Resistances
Shorthand notation for parallel
1 1 1 1 3
TR R R R R
5 11 7
3 3T
R . kR . k
Adding Additional Branches
• The addition of a parallel branch decreases the resistance of the circuit
• single branch in (a) draws 5mA from the source• additional branch in (b) increases the current
drawn from the source to 10mA
Vs8 V
R11kOhm
R2200 Ohm
Vs12 V
R11.5kOhm
R23kOhm
Determine the branch currents and the total current for each circuit. Check with MultiSim.
TEAM ACTIVITY
top related