Table of Contents
Advertisement
Chapter 4 Electrical System
Section 1 Basic Knowledge
In order to get a further understanding of structure and working principle of motorcycle electrical
system,you should have a general conception about basic knowledge of electrics firstly.
1 Electricity,electric current,voltage and resistance
The basic component of any substance is atom.There exists electropositive atomic nucleus and
electronegative electron inside the atom.The quantity of nucleus is the same as electron,so which makes
the positive electricity counteract the negative electricity and causes atom to be neutral.If the substance is
influenced for friction or magnetic field,this balance will be broken.So the electron will increase or decrease
because of moving.At that time,the substance has electric charge because the atom is not neutral.The
electric charge of substance has the relationship with the increasing and decreasing of atom.When the
atom increases,the substance will be electronegative.When the atom decreases,the substance will have
positive electricity.
Electric charge moves regularly in conductor along a stated direction,which is called electric current.The
quantity of electric charge per second is used to scale the strength of electric current.In electrics,we use I
to stand for electric current.Its strength unit is Amp(A).Normally,the stated direction of electric current is
from the anode of battery to the cathode.
There is an interaction force between electric charge.In order to make electric charge move,such force must
be overcome. When moving the positive charge,the work for conquering the force between electric charge
is called potential.The differential potential between any two points is called voltage.We use U to stand for
and its unit is V.
When electric current flows in a substance,the substance will produce a resistance,which is called
electric resistance.We use R to stand for,its unit is Ω.Different substance has different resistance.For
example,the resistance of copper,iron,aluminium is small,which is called conductor.However,the resistance
of wood,china,plastic is big,which is called dielectric.Also,there are some other substances,such as
silicon,whose electric performance is between conductor and dielectric,which is called semiconductor.
2 Ohm's Law
Ohm's law indicates the relationship among voltage,resistance and electric current.Viz.Electric current(I)
and voltage(U) have direct proportion and electric current(I) and resistance(R) have inverse proportion.Its
formula is I=U/R,Also,U=IR,R=U/I.
3 Electric apparatus,direct current(DC),alternating current(AC) and electrical source
Electric apparatus is usually called load,which is an equipment that can consume electric power and
transfer the power to other kind of power.
The device which offers power to electric apparatus is called electrical source or power supply.
The electric current what electrical source offers to electric equipment has two types:One type whose
intensity and direction don't change according to the change of time is called direct current(DC).The other
one whose intensity and direction change periodically according to the change of time is called alternating
current(AC).
4 Circuit,series circuit and parallel circuit
The closed circuit which is made up of electrical source,electric apparatus and connecting lead is called
circuit.The circuit is divided into two basic types:series circuit and parallel circuit.In series circuit,several
electric apparatuses connect with each other and there is no cut in the middle.At this time,the electric
current which is through each electric apparatus is the same.But in parallel circuit,the beginning and the
end of each equipment connects between the two points and the voltage of two end is the same.In the
complicated circuit of motorcycle,both series circuit and parallel circuit coexist.
5 Short circuit and open circuit
In a normal circuit,if two leads,of which electrical source passes electric apparatus,don't pass electric
apparatus and connect with each other,which is called short circuit.In the circuit which is made up of
electrical source,electric apparatus and connecting lead,because of the cut of lead,it makes electric current
not form a closed circuit,which is called open circuit.
6 Left-hand rule and right-hand rule
In the magnetic field which can produce electromagnetism induction,stretch out the left hand,make palm
flat,make thumb plumb the other four fingers,let magnetic line plumb and get through the center of palm
and make four fingers towards the direction of electric current.At this time,the direction which thumb
points to is the direction of magnetic field power,which is called left-hand rule.
Unwind the thumb of right hand,hold coil along the direction of electric current with the other four fingers.
At this time,the direction which the thumb points to is the direction of magnetic wire which coil produces
47
magnetic field,which is called right-hand rule.
Hide quick links:
Advertisement
Table of Contents
