Page 276 - 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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260 Automobile mechanical and electrical systems

Figure 3.3 Heating effect

Figure 3.4 Chemical effect

The movement from negative to positive is called the electron fl ow. However, it
Defi nition was once thought that current fl owed from positive to negative. This convention
is still followed for practical purposes. Therefore, even though it is not correct,
Current fl ow the most important point is that we all follow the same convention. We say that
Conventional current fl ow is from current fl ows from positive to negative.
positive to negative.
When a current fl ows in a circuit, it can produce only three effects: heat,
chemical and magnetic ( Figs 3.3–3.6 ). The heating effect is the basis of electrical
components such as lights and heater plugs. The chemical effect is the basis for
electroplating and battery charging. The magnetic effect is the basis of relays,
motors and generators. The three effects are reversible. For example, electricity
can make magnetism, and magnetism can be used to make electricity.

The number of electrons through a circuit ( Fig. 3.7 ) in every second is the rate of
Defi nition
fl ow. The cause of electron fl ow is the electrical pressure. A lamp, for example,
Rate of fl ow produces an opposition to the rate of fl ow set up by the electrical pressure.
The number of electrons passing Power is the rate of doing work or changing energy from one form to another. If
through a circuit in 1 second. the voltage applied to the circuit was increased but the lamp resistance stayed
the same, then current would increase. If the voltage was kept constant but the
lamp was changed for one with a higher resistance, then current would decrease.