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Thermionic emission: It is the effect in which when a metal is heated, some of the ‘free’ electrons gain enough kinetic energy to escape from the metal surface.
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Cathode-Ray Oscilloscope
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The component to be tested (e.g., a resistor or a mic) is connected across “Y-inputs”.
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Controls
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“Gain” control adjusts the volts per division vertically
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“Timebase” control adjusts the milliseconds per division horizontally
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“Y-offset” control moves the waveform up or down
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“X-offset” control moves the waveform left or right
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Circuit components
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Resistor: Its purpose is to limit the flow of current.
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Colour-code: A resistor has colour bands to show its resistance and tolerance.
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For example, this is a 1500 Ω resistor:
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Power rating of a resistor: It is the maximum amount of electrical energy per second (J/s or W) that the resistor can convert into heat without getting damaged.
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Usually power rating depends on the size of the resistor.
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Using resistors with large power ratings means that they will occupy more space on the circuit board.
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Using resistors with lower (just enough) power ratings means that they may become damaged easily due to small fluctuations.
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Thermistor: Its resistance decreases as the temperature increases.
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Light-dependent resistor (L.D.R.): Its resistance decreases as brightness of light increases.
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Capacitor: It can store charge. It takes time to get fully charged but then it can discharge instantly. Therefore, it has use in time-delay circuits.
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Potential division
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When resistors are connected in series, each resistor gets a share of the e.m.f. according its share of the total resistance.
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For example, if three resistors R1, R2 and R3 are connected in series then potential difference across R1 can be calculated as:
V1 = ( R1 / (R1 + R2 + R3) ) x e.m.f.
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