BASIC LAWS

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BASIC LAWS

• Ohms Law

• Kirchhoffs Law

• Series resistors voltage division

• Parallel resistors current division

• Y -?? transformation

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Ohms Law
Property of a material to resist a flow of
current known as resistance
- measured in ohms (?)
Mathematically,
- Resistivity of the material
- length of the material
- Cross section area of the material
V ?
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Ohms Law
Ohmss Law A voltage across a resistor is
directly proportional to the current flowing
through a resistor
V ?
v ? i
Constant of proportionality between v and i is
the resistance, R (?)
v i R
Must comply with passive sign convention
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Ohms Law
Fixed resistors
Wirewound type
carbontype type
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Ohms Law
Variable resistors
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Ohms Law
Two extreme values of resistance
Short circuit
Open circuit
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Ohms Law
Conductance reciprocal of resistance
- measured in siemens (S)
Conductance ability of an element to conduct
current
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Ohms Law
Power in a Resistor
Always positive
Always absorbs power
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Kirchhoffs Law
Network topology
A branch represents a single element such as a
voltage source or a resistor.
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Kirchhoffs Law
Network topology
A branch represents a single element such as a
voltage source or a resistor.
A node is the point of connection between two
or more branches.
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Kirchhoffs Law
Network topology
A branch represents a single element such as a
voltage source or a resistor.
A node is the point of connection between two
or more branches.
A loop is any closed path in a circuit.
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Kirchhoffs Law
Network topology
Two or more elements are in series if they
exclusively share a single node and consequently
share the same current
Two or more elements are in parallel if they are
connected to the same two nodes and consequently
have the same voltage across them
1? 2? - parallel
10V 4? - parallel
5? in series with (1? and 2 ? in parallel)
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Kirchhoffs Law
Kirchhoffs Current Law (KCL)
Kirchhoffs current law (KCL) states that the
algebraic sum of currents entering a node (or a
closed boundary) is zero
Mathematically,
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Kirchhoffs Law
Kirchhoffs Voltage Law (KVL)
Kirchhoffs voltage law (KVL) states that the
algebraic sum of all voltages around a closed
path (or loop) is zero.
Mathematically,