ELEC 0002 : Introduction to Electrical Engineering
UCL
Year 1
Term 1
, Dc circuits
1) ecibel
pout
1010910 Pin 2010910 Vor
Circuit Basics
·
current
·
in metals are carried by electrons
dQ
·
in semiconductors can be carried by both electrons and holes I =
dt
·flows from positive to
negative potential
·
resistance
·opposition to current flow R =
E R =
·
resistivity of metals increase as temperature increases
·
impure metals have greater resistivity than pure metals
·
resistivity of semiconductors decrease with increasing temperatures
·resistivity is determined by number of carriers which is smaller than metals
resistors in series: Ri k, =
+ R2 + R3 +...
·
resistors in parallel: R +*s = ++...
·
conductance
·
inverse of resistance G =
H
·conductivity is inverse of resistivity 0 0
=
·
Ohm's Law
·
current flowing between 2 points is directly proportional to the potential difference
·
ohmic behaviour is when resistance is constant
·
ENF
a potential difference created in some
way from another form of
energy
·
·
at open circuit full ENF is measured
·
atclosed circuit, V:E-Ir E=EMF r= internal resistance
·
potential and potential difference
·
electrostatic potential exists at each point in the circuit
·voltmeters only measures potential differences between two points
power dissipation
·
P: IV =
= ICR
·
PCR if current is constant
·Pc* if voltage is constant
Kirchhoff's Law
·
First law
·
the algebraic sum of currents flowing at anode of a circuit is zero [I = 0
·secondlaw
·
sum of voltages around a closed loop is zero [CEMFS -
IR products) 0 =
·
Mesh analysis (for currents)
·
Divide the circuit into a mesh of loops each carrying a current
·
apply Kirchhoff's and Law to each loop to get a set of simultaneous equations and solve the equations
·
Nodal analysis (for voltage)
·
choose one node as v0
=
and figure out all the potentials we can at other nodes
·
Un will be the only unknown potential and use Kirchhoff's 1st law to solve for Un
S uperposition Theorem
·
the response in any branch of a linear circuit having more than one source equals the sum of the responses caused
by each source acting alone when all the other sources are replaced by just their internal resistances
·
a component is linear when its output is proportional to its input
·linear components: capacitors and resistors
·
non-linear components: diode
UCL
Year 1
Term 1
, Dc circuits
1) ecibel
pout
1010910 Pin 2010910 Vor
Circuit Basics
·
current
·
in metals are carried by electrons
dQ
·
in semiconductors can be carried by both electrons and holes I =
dt
·flows from positive to
negative potential
·
resistance
·opposition to current flow R =
E R =
·
resistivity of metals increase as temperature increases
·
impure metals have greater resistivity than pure metals
·
resistivity of semiconductors decrease with increasing temperatures
·resistivity is determined by number of carriers which is smaller than metals
resistors in series: Ri k, =
+ R2 + R3 +...
·
resistors in parallel: R +*s = ++...
·
conductance
·
inverse of resistance G =
H
·conductivity is inverse of resistivity 0 0
=
·
Ohm's Law
·
current flowing between 2 points is directly proportional to the potential difference
·
ohmic behaviour is when resistance is constant
·
ENF
a potential difference created in some
way from another form of
energy
·
·
at open circuit full ENF is measured
·
atclosed circuit, V:E-Ir E=EMF r= internal resistance
·
potential and potential difference
·
electrostatic potential exists at each point in the circuit
·voltmeters only measures potential differences between two points
power dissipation
·
P: IV =
= ICR
·
PCR if current is constant
·Pc* if voltage is constant
Kirchhoff's Law
·
First law
·
the algebraic sum of currents flowing at anode of a circuit is zero [I = 0
·secondlaw
·
sum of voltages around a closed loop is zero [CEMFS -
IR products) 0 =
·
Mesh analysis (for currents)
·
Divide the circuit into a mesh of loops each carrying a current
·
apply Kirchhoff's and Law to each loop to get a set of simultaneous equations and solve the equations
·
Nodal analysis (for voltage)
·
choose one node as v0
=
and figure out all the potentials we can at other nodes
·
Un will be the only unknown potential and use Kirchhoff's 1st law to solve for Un
S uperposition Theorem
·
the response in any branch of a linear circuit having more than one source equals the sum of the responses caused
by each source acting alone when all the other sources are replaced by just their internal resistances
·
a component is linear when its output is proportional to its input
·linear components: capacitors and resistors
·
non-linear components: diode
