ENG1002 Lecture Notes - Lecture 5: Voltage Divider
30 May 2018
School
Department
Course
Professor
Q"="it
E"="QV
(nodes)
(branches)
Mathematically,"each"of"the"labelled"voltages"is"determined"as"the"voltage"at"the"
+terminal"subtract the"voltage"at"the"-terminal."(acc"to"passive"power"
convention)
(40"||"60)||"16"works,"but"NOT"40"||"60"||"16!!
(each"is"3V"because"of"6Ohm"resistor"below"that"current"has"to"pass"
through"regardless,"resistance"doesn't"matter"here)
**don't"use"Ohm's"Law"to"find"voltage"v2,"but"KVL."Ohm's"Law only"for"
total"current"(which"is"not"being"measured"by"the"device)
Voltage"changes"in"series"circuit
Current"changes"in"parallel" circuit
(NOT
Taking"frm"centre"node,
0"="-Va"+"15V"+"10V)
Use"loops"for"KVL
Use"nodes"(v1,"v2"etc)"for"KCL
Taking"in-flowing"currents"as"positive
Take"entire"top"line"as"a"node!
Use"that"as"ONE"node"for"KCL.
Meaning"0"="all"four"wires
0"="-4"+"v/5"+"v/15"+"2
Find"i1using"Ohm's"Law1.
Find"current"through"each"resistor"using"
Ohm's"Law
2.
Find"i2using"KCL3.
Find"voltage" using"KCL1.
Find"i1and"i2using"Ohm's"Law2.
Find"power"through"ALL"FOUR"
circuit" elements" using"P"=" VI"
(delivering/absorbing" infer"
through"direction/+-signs)
3.
Voltage division"formula"-ACTUAL"one
Current division"formula"-OTHER"one
**for"TWO"parallel" circuit"resistors"only!!
No"need"to"consider"R1
Just"use"R2and"R3.
Find"v3using"volt-div"formula
-remembering"that"pd"is"5-(-5),"not"5!
Thus,"v3"="6V
Find"v0using"v3"
Thus,"v0"="-5+6-0"="1V
VERYY"common"mistake!
Choose"nodes"(VAand"VBetc)"
according"to"what"you"need"to"find
Week$5
Thursday," 20"April"2017
19:02
Q"="it
E"="QV
(nodes)
(branches)
Mathematically,"each"of"the"labelled"voltages"is"determined"as"the"voltage"at"the"
+terminal"subtract the"voltage"at"the"-terminal."(acc"to"passive"power"
convention)
(40"||"60)||"16"works,"but"NOT"40"||"60"||"16!!
(each"is"3V"because"of"6Ohm"resistor"below"that"current"has"to"pass"
through"regardless,"resistance"doesn't"matter"here)
**don't"use"Ohm's"Law"to"find"voltage"v2,"but"KVL."Ohm's"Law only"for"
total"current"(which"is"not"being"measured"by"the"device)
Voltage"changes"in"series"circuit
Current"changes"in"parallel" circuit
(NOT
Taking"frm"centre"node,
0"="-Va"+"15V"+"10V)
Use"loops"for"KVL
Use"nodes"(v1,"v2"etc)"for"KCL
Taking"in-flowing"currents"as"positive
Take"entire"top"line"as"a"node!
Use"that"as"ONE"node"for"KCL.
Meaning"0"="all"four"wires
0"="-4"+"v/5"+"v/15"+"2
Find"i1using"Ohm's"Law1.
Find"current"through"each"resistor"using"
Ohm's"Law
2.
Find"i2using"KCL3.
Find"voltage" using"KCL1.
Find"i1and"i2using"Ohm's"Law2.
Find"power"through"ALL"FOUR"
circuit" elements" using"P"=" VI"
(delivering/absorbing" infer"
through"direction/+-signs)
3.
Voltage division"formula"-ACTUAL"one
Current division"formula"-OTHER"one
**for"TWO"parallel" circuit"resistors"only!!
No"need"to"consider"R1
Just"use"R2and"R3.
Find"v3using"volt-div"formula
-remembering"that"pd"is"5-(-5),"not"5!
Thus,"v3"="6V
Find"v0using"v3"
Thus,"v0"="-5+6-0"="1V
VERYY"common"mistake!
Choose"nodes"(VAand"VBetc)"
according"to"what"you"need"to"find
Week$5
Thursday," 20"April"2017 19:02
