Resistor values
Resistors are coded with coloured bands to ease the problem of marking such small components.
The number corresponding to ten colours is used and the values per position.
For example, 180 000 ohms is coded with the first digit brown, then grey and finally yellow. The fourth band indicates the tolerance that the value has with respect to the stated value. For example, silver indicates 10% tolerance, meaning that the 180 000 ohms could vary between 180 000+-18 000, i.e. 162 000 to 198 000.
Those tolerances may seem to reflect poor manufacture but in most circuits they are, in fact, quite satisfactory. Relaxing the tolerance enables the maker to sell them more cheaply.
3. Fill in the missing colours in this table with the help of the text.
4. Find the values and tolerance of resistors banded as follows:
1. red violet orange silver
2. blue grey brown gold
3. green blue red silver
4. red red green _____
5. brown black orange _____
6. orange orange brown gold
5. Answer the questions below:
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Why are resistors coded with coloured bands rather than some other form of marking?
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What would be the effect of making resistors with a much higher tolerance?
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Between which values might a resistor marked green, blue, orange and silver vary?
Capacitors and Capacitor Values
Capacitors are components that are used to store an electrical charge and are used in timer circuits. A capacitor may be used with a resistor to produce a timer. Sometimes capacitors are used to smooth a current in a circuit as they can prevent false triggering of other components such as relays. When power is supplied to a circuit that includes a capacitor - the capacitor charges up. When power is turned off the capacitor discharges its electrical charge slowly. A capacitor is composed of two conductors separated by an insulating material called a DIELECTRIC. The dielectric can be paper, plastic film, ceramic, air or a vacuum. The plates can be aluminium discs, aluminium foil or a thin film of metal applied to opposite sides of a solid dielectric. The CONDUCTOR - DIELECTRIC - CONDUCTOR sandwich can be rolled into a cylinder or left flat. A capacitor functions much like a battery, but charges and discharges much more efficiently. Capacitor electron storing ability (capacitance) is measured in Farads. Capacitors are used in virtually every area of electronics, and they perform a variety of different tasks.
There are many different types of capacitor. Each capacitor type has its own advantages and disadvantages and therefore the uses of the capacitor can be different.
Diodes
A diode allows electricity to flow in one direction only and blocks the flow in the opposite direction.
There are different types of diode but their basic functions are the same.
The electronic equivalents of one-way streets, diodes allow an electric current to flow through them in only one direction. They are also known as rectifiers. Diodes can be used to change alternating into direct currents. There is a host of different types of diode that are manufactured and used in today's electronics. Each type has different properties and this makes them suitable for different applications or jobs.
Whatever the type of diode, the basic idea of the diode is important in the electronics industry today, whether it be used for the production of commercial or industrial equipment, of for use by the hobbyist, or anyone studying electronics.
6. Answer the following questions:
1. What are electronic circuits built up from?
2. What are the functions of capacitors?
3. What is a measurement unit of capacitance?
4. What are essential parts of capacitors?
5. What does the use of a capacitor depend on?
6. Why are diodes also called rectifiers?
7. What is the main function of diodes?
7. Complete the sentences:
1. All electronic components are depicted as….in a circuit diagram.
2. The most important electronic components are…..
3. A capacitor can be used…….
4. The dialectric material used in capacitors are……
5. A diode allows…..
8. Translate the following words and word-combinations into English:
Схема, маркування, конденсатор, кольорова стрічка, величина(значення), зберігати, випрямляти, постійний струм, електричний заряд, запобігати, заряджатися, потужність, розряджатися, застосування, виконувати
9. Translate the sentences into Ukrainian:
1. Resistors are coded with coloured bands to ease the problem of marking small components.
2. The fourth band of a resistor code corresponds to the tolerance.
3. Relaxing the tolerance the maker may sell the resistor cheaply.
4. The first three bands of a capacitor code are the same as of a resistor coding.
5. The classification of semiconductor diode employs either two letters and three figures.
6. Zener diodes have an additional letter which denotes the tolerance of the zener voltage.
TEXT B