Signals and Systems
Boise State University
Electric Circuits
Electric Circuits
Chalmers
Chalmers
Communications
Systems Group,
Hani
Mehrpouyan,
Signals and Systems,
Communications Systems Group,
Signals and Systems,
Chalmers University of Technology,
Department of
Electrical and Computer Engineering,
Chalmers University
of Technology,
Sweden
Boise State
University
Sweden
c 2010
Lecture 2 (Ohm’s Law
&
c 2010 Circuit Elements)
Aug 26th, 2015
August 20, 2015
August 20, 2015
Hani Mehrpouyan (hani.mehr@ieee.org)
Hani Mehrpouyan (hani.mehr@ieee.org)
Boise State c 2015
Boise State c 2015
1
1
1
Signals and Systems
Boise State University
Overview
Electric Circuits
• Ohm’s law: a central concept in electric
circuits.
Chalmers
Communications Systems Group,
Signals and Systems,
• Resistors
Chalmers University of Technology,
Sweden
c 2010
August 20, 2015
Hani Mehrpouyan (hani.mehr@ieee.org)
Boise State c 2015
22 1
Signals and Systems
Boise State University
Resistivity
Electric Circuits
• Materials tend to resist the flow of
electricity through them.
Chalmers“resistance”
• This property is called
Communications Systems Group,
• The resistanceSignals
of an
object is a function
and Systems,
Chalmers University of Technology,
of its length,
l, andSweden
cross sectional area,
A, and the material’s
resistivity:
c 2010
August 20,
l 2015
R=ρ
Hani Mehrpouyan (hani.mehr@ieee.org)
A
33 1
Boise State c 2015
Signals and Systems
Boise State University
Ohm’s Law
Electric Circuits
• In a resistor, the voltage across a resistor is
directly proportional to the current flowing
through it.
V Chalmers
= IR
Communications Systems Group,
Signals and Systems,
• The resistance
of an element is measured in
Chalmers University of Technology,
units of Ohms, Ω, (V/A)
Sweden
c 2010
• The higher the resistance,
the less current will
flow through for a
given
voltage.
August 20, 2015
• Ohm’s law requires conforming to the passive
sign convention.
Hani Mehrpouyan (hani.mehr@ieee.org)
Boise State c 2015
44 1
Signals and Systems
Boise State University
Resistivity of Common
Materials
Electric
Circuits
Chalmers
Communications Systems Group,
Signals and Systems,
Chalmers University of Technology,
Sweden
c 2010
August 20, 2015
Hani Mehrpouyan (hani.mehr@ieee.org)
55 1
Boise State c 2015
Signals and Systems
Boise State University
Short and Open Circuits
Electric
Circuits
• A connection
with almost
zero
resistance is called a short circuit.
• Ideally, any current may flow through the
Chalmers
short.
Communications Systems Group,
Systems,
• In practice thisSignals
is aand
connecting
wire.
Chalmers University of Technology,
• A connection with Sweden
infinite resistance is
c 2010
called an open circuit.
20, 2015
• Here no matterAugust
the voltage,
no current
flows.
Hani Mehrpouyan (hani.mehr@ieee.org)
Boise State c 2015
66 1
Signals and Systems
Boise State University
Linearity
Electric Circuits
• Not all materials obey Ohm’s
Law.
• Resistors that do are called
Chalmers
linear resistors because
their
Communications Systems
current voltage relationship
is Group,
Signals and Systems,
always linearly Chalmers
proportional.
University of Technology,
Sweden
• Diodes and light bulbs are
c 2010
examples of non-linear
elements.
August 20, 2015
Hani Mehrpouyan (hani.mehr@ieee.org)
77 1
Boise State c 2015
Signals and Systems
Boise State University
Power Dissipation
Electric Circuits
• Running current through a resistor
dissipates power.
v2
Communications Systems
R Group,
p = viChalmers
= i2 R =
Signals and Systems,
Chalmers University of Technology,
• The power dissipated
Sweden is a non-linear
2010voltage
function of current cor
• Power dissipated
is 20,
always
August
2015 positive
• A resistor can never generate power
Hani Mehrpouyan (hani.mehr@ieee.org)
Boise State c 2015
88 1
Signals and Systems
Boise State University
Electric Circuits
Chalmers
Communications Systems Group,
Signals and Systems,
Chalmers University of Technology,
Sweden
c 2010
August 20, 2015
Hani Mehrpouyan (hani.mehr@ieee.org)
Boise State c 2015
9
1
Signals and Systems
Boise State University
Electric Circuits
Chalmers
Communications Systems Group,
Signals and Systems,
Chalmers University of Technology,
Sweden
c 2010
August 20, 2015
Hani Mehrpouyan (hani.mehr@ieee.org)
Boise State c 2015
10 1
Signals and Systems
Boise State University
Electric Circuits
Chalmers
Communications Systems Group,
Signals and Systems,
Chalmers University of Technology,
Sweden
c 2010
August 20, 2015
Hani Mehrpouyan (hani.mehr@ieee.org)
Boise State c 2015
11 1
Signals and Systems
Boise State University
Electric Circuits
Chalmers
Communications Systems Group,
Signals and Systems,
Chalmers University of Technology,
Sweden
c 2010
August 20, 2015
Hani Mehrpouyan (hani.mehr@ieee.org)
Boise State c 2015
12 1
Signals and Systems
Boise State University
Electric Circuits
Chalmers
Communications Systems Group,
Signals and Systems,
Chalmers University of Technology,
Sweden
c 2010
August 20, 2015
Hani Mehrpouyan (hani.mehr@ieee.org)
Boise State c 2015
13 1
Signals and Systems
Boise State University
Electric Circuits
Chalmers
Communications Systems Group,
Signals and Systems,
Chalmers University of Technology,
Sweden
c 2010
August 20, 2015
Hani Mehrpouyan (hani.mehr@ieee.org)
Boise State c 2015
14 1
Signals and Systems
Boise State University
Electric Circuits
Chalmers
Communications Systems Group,
Signals and Systems,
Chalmers University of Technology,
Sweden
c 2010
August 20, 2015
Hani Mehrpouyan (hani.mehr@ieee.org)
Boise State c 2015
15 1