Accueil Mecanique Electricité Optique Chimie Matière
Mesures et lois des circuits
PCCL © 201
PCCL © 201
What is an electrical circuit?
Simple electrical circuit with a
single lamp or a motor:
Simple electrical circuit loop
generator, switch, lamp, motor, LED, diode, son of connection resistance
(ohmic conductors), limiting itself, besides the switches to a generator and
Influence of the order and number of components other than the generator.
Series and parallel bulbs
The electrical circuit comprising leads.
Back to the short circuit: the distinction between short-circuit of a
generator and short circuit of a lamp.
LAWS OF CURRENT
Current and voltage
Introduction procedure of intensity and
Experimental approach to the "resistance"
The model of the component derived ohmic
- Conduction and electrical structure of matter
The electron: understanding the electrical conduction in metals
All metals conduct electricity. All solids do not conduct electrical current. Electrical conduction in metals is interpreted by moving electrons.
- The ion: Understanding the electrical conduction in aqueous solutions
aqueous solutions do not conduct electrical current.
- ELECTRICITY AND AC (alternative current) ELECTRICAL CIRCUITS
- From the power plant to the user
The alternator is the
part common to all power plants.
Tension, time-varying, can be obtained by moving a magnet near a coil.
DC and AC voltage periodically
DC voltage and
variable over time, periodic alternating voltage.
and / or acquisition interface, the instrument measures the voltage and
This effective value is proportional to the maximum value.
- Electrical Power and Energy
Power : rated
power a device.
: Energy: Electrical energy E transferred for a time t to a unit rated
power P is given by the relation
- ELECTRICAL AND DC - Transfers of energy in a
generator and a receiver. Electric power We received
by a receiver, through which the current I, during
- ELECTRICAL AND DC
- Transfers of energy in a generator and a receiver.
Electric power We received by a receiver, through which the current I, duringΔt :
We = (VA-VB) IΔt
with UAB = (VA-VB) > 0.
Electrical power transfer:
P = UABI.
Joule effect : applications
Electrical energy transferred from the electric generator to the rest of the circuit during Δt :
We = (VP-VN) I Δt
= UPN means the voltage between the positive and negative
terminals of the generator and I the current passing through it.
P = UPN I
Summary of energy transfer during Δt
electrical energy UAB I
, and "clears" some r.I2.Δt
and converts the rest in another form (mechanical, chemical ...).
Complement r.I2.Δt is dissipated as heat by Joule effect.
- Behavior of a global circuit
Distribution of electric power during Δt :
We(generator) = ΣWe(receivers)
Justification energy additivity law of tension and intensity (node or junction law = Kirchhoff's Law) .
parameters affecting the energy transferred by the generator to the
rest of a resistive cicuit:
- Maximum power available at the terminals of a generator, tolerated by a receiver.
- MAGNETISM. ELECTROMAGNETIC FORCES
Action of a
magnet, a current, a very short needle.
Magnetic field created by a current
the field value B and the current in the absence of magnetic media.
Laplace's law :
management, direction, value of the force: F = I.l .B.sinα
Conversion of electrical energy into mechanical energy. Role of Laplace forces. Observation of the effect associated with the reciprocal motion of a circuit in a magnetic field: conversion of mechanical energy into electrical energy.
- Changes in electrical systems
In case of a component RC
relationship for a capacitor i = dq/dt, q capacitor charge in
Component response of a
RC to a level of voltage: voltage across the capacitor, the current
intensity, experimental and theoretical study (analytical solution).
In case of a RL component
Brief description of a
u = ri + L di /dt
Inductance: the unity henry (H).
Current response of a
coil to a voltage step: experimental and theoretical study (analytical
T0 = 2 Π √ LC
Maintenance of oscillations.
- To produce signals to communicate
Electromagnetic waves, medium of choice to transmit information
Transmission of information
examples, show that the simultaneous transmission of several information
requires a "channel" assigned to each.
The electromagnetic waves
Propagation of an
electromagnetic wave in vacuum and material media in many ...
Module of a sinusoidal voltage
u(t) = Umax cos(2πft + Φ0)
Parameters can be modulated: amplitude, frequency and / or phase.
2. Amplitude modulation
2.1 principe de la modulation d'amplitude
voltage: voltage whose amplitude is linear function of the modulating
Principle of the amplitude demodulation
Functions to be
performed to demodulate an amplitude modulated voltage.
Realization of a disposotif to receive a radio amplitude modulation
The component coil capacitor connected in parallel experimental study, by
modeling a parallel LC circuit.