Page 292 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

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Electrical systems 275

It is the magnetic effect of the changes in current fl ow that gives this device the
properties of inductance. The inductor is also used as a fi lter because it tends to
prevent changes in signals.
Integrated circuits (ICs) are constructed on a single slice of silicon ( Fig. 3.36 ).
Combinations of thousands or even millions of the components mentioned
previously can be combined to carry out various tasks. These tasks can range
from a simple switching action to the operation of a microprocessor of a
Figure 3.36 Integrated circuit (IC)
computer. The components required for these circuits can be made directly on
package
to one slice of silicon. The advantage of this is not just the size of the ICs (which
can be very small) but the speed at which they can be made to work.

3.2 Engine electrical

3.2.1 Batteries

A good supply of electric power is necessary for modern vehicles. The engines
require a large current to operate the starter motor and many other systems are
Defi nition
electrically powered. All modern cars use a 12 V system. The majority of vehicle
batteries are of conventional design, using lead plates in a dilute sulphuric acid Direct current (d.c.)
electrolyte ( Fig. 3.37 ). This feature leads to the common description of ‘lead-acid’ Current that moves in a single
direction in a steady fl ow.
batteries. The output from a lead-acid battery is direct current (d.c.).
A rechargeable battery is an electrochemical unit that converts an electric current
into a modifi ed chemical compound. This chemical reaction can be reversed
to release an electric current. The modifi ed chemical compound in the battery
stores energy, which is available as electricity when connected to a circuit.
Defi nition
A few batteries have open cells that require routine maintenance to the
electrolyte level. This usually consists of adding distilled water at regular Alternating current (a.c.)
intervals. Most modern lead-acid battery designs have improved plate This is often used to indicate an
construction and case design, which with precise alternator charge control alternating potential rather than a
allows maintenance-free types to be used. current, as in 240 V or 110 V a.c.
A vehicle 12 V battery is made up from six cells. Each lead-acid cell has a nominal
voltage of 2.1 V, which gives a value of 12.6 V for a fully charged battery under no-
load conditions. The six cells are connected in series, internally in the battery, with
lead bars. The cells are formed in the battery case and are completely separate

Figure 3.37 Vehicle battery. (Source: Bosch Media)