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Basics of Electricity
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If any two of the electrical
characteristics are known, the equation can be transposed to calculate the value of the unknown
characteristic.
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If the unknown factor is voltage,
multiply current times resistance:
E = I x R.
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If the unknown factor is current,
divide the voltage by the resistance:
I = E/R.
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If the unknown factor is
resistance, divide voltage by the current:
R = E/I.
For example, an electrical circuit in which voltage is 240 volts and the resistance of a
light bulb is 960 ohms, then the current is 0.25 amps as shown by the calculation in
Figure1.8.
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Figure 1.8. Example of Ohm's Law.
Using the previous example (except the resistance of the light bulb is unknown), divide
voltage by current to find resistance is 960 ohms as shown in
Figure 1.9.
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Figure 1.9. Ohm's Law used to calculate resistance.
As mentioned previously, there are good and poor conductors of electricity.
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Good conductors include copper,
silver, and aluminium.
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Poor conductors, including rubber,
plastic, cloth and mica, are known as insulators.
The electrical conductor in the electrical circuit, such as a copper wire, is covered by an
insulation material to prevent any person touching a bare conductor and receiving a severe shock.
See
Figure 1.12. Insulation material is also used to prevent two bare wires from
touching each other and causing a short circuit. Short circuits will be discussed in more detail
later.
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Figure 1.12. Electrical conductor covered with insulation.
An electrical circuit can be arranged in one of three circuit designs: series, parallel, and
series- parallel.
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