lecture 2 kirchhoff’s law
TRANSCRIPT
KIRCHHOFF’S LAW
Lecture 2
Maha K. Omar
OVERVIEW
Ohm’s Law
R the circuit resistance
V the potential difference across R
I is the current flowing through R
RIV
Electric power P
Electric Energy W
R
V
RI
VIP
2
2
tPW
SERIES CIRCUIT
Two Elements are said to be in series if they are
connected at a single point and if there are no
other current carrying connections at this point.
Current is the same everywhere in a series circuit.
KIRCHHOFF’S VOLTAGE LAW
The summation of voltage rises and voltage drops around a closed loop is equal to zero
0V
0321 VVVE
PROBLEM
Verify Kirchhoff’s voltage law
SERIES TOTAL RESISTANCE
321
321321
321 0
RRRR
RIE
RIRIRIVVVE
VVVE
tot
tot
PROBLEM Find
Total resistance
Current (direction and magnitude)
Potential across each resistor
Power dissipated by each resistor
Power delivered by the voltage source
Compare the last two quantities
PARALLEL CIRCUIT
Elements or branches of elements are said to be in a parallel connection when they share exactly the same two nodes.
The voltage across all parallel elements is the same.
KIRCHHOFF’S CURRENT LAW
The summation of currents entering a node is equal to the summation of currents leaving the node
leavingentering II
43251 IIIII
PROBLEM
Verify Kirchhoff’s current law
PARALLEL TOTAL RESISTANCE
321
321
321
1111
RRRR
R
E
R
E
R
E
R
E
IIII
T
T
T
PROBLEM
Find
total resistance
Total current
Power delivered by the voltage source
Current in each resistance
Power dissipated by each resistance
QUIZ
Find vab when:
Rx=0
Rx=15 KΩ
Rx=∞