WEBVTT NOTE Reading Schematics and Naming Circuit Blocks 1 00:00:00.000 --> 00:00:02.383 What a schematic shows. 2 00:00:02.383 --> 00:00:09.758 Question. What is an electrical diagram using standard component symbols called? 3 00:00:10.658 --> 00:00:13.144 Answer. Schematic. 4 00:00:13.744 --> 00:00:20.831 Question. Which of the following is accurately represented in electrical schematics? 5 00:00:21.731 --> 00:00:25.291 Answer. Component connections. 6 00:00:25.891 --> 00:00:44.350 Connections, and nothing else. A schematic does not show physical placement, wire lengths, or the size of anything. Two components drawn adjacent may be at opposite ends of a chassis; a long wire may be a short line. 7 00:00:44.350 --> 00:00:57.852 What the schematic promises is which terminal joins which. The three pool diagrams. Twelve of the T6 questions point at three figures published with the pool. 8 00:00:57.852 --> 00:01:11.013 They are worth opening now and coming back to, because the questions ask nothing more than "what is component n". Figure T-1, a simple transistor circuit. 9 00:01:11.013 --> 00:01:29.728 This question refers to one of the exam's circuit diagrams, which you will need to look at in the written lesson. Component, 1; What it is, Resistor. Component, 2; What it is, Transistor. Component, 3; What it is, Lamp. 10 00:01:29.728 --> 00:01:45.623 Component, 4; What it is, Battery. And a function question on the same figure: the function of component 2 (the transistor) is to control the flow of current. Figure T-2, a power supply. 11 00:01:45.623 --> 00:02:03.655 This question refers to one of the exam's circuit diagrams, which you will need to look at in the written lesson. Component, 3; What it is, Single-pole single-throw switch. Component, 4; What it is, Transformer. 12 00:02:03.655 --> 00:02:18.781 Component, 6; What it is, Capacitor. Component, 8; What it is, Light-emitting diode. Component, 9; What it is, Variable resistor. Figure T-3, a tuned circuit feeding an antenna. 13 00:02:18.781 --> 00:02:32.283 This question refers to one of the exam's circuit diagrams, which you will need to look at in the written lesson. Component, 3; What it is, Variable inductor. 14 00:02:32.283 --> 00:02:47.916 Component, 4; What it is, Antenna. The symbols worth recognising on sight. Rather than memorising numbered components, learn the shapes: Resistor, zigzag (US) or plain rectangle (IEC). 15 00:02:47.916 --> 00:03:02.359 Capacitor, two parallel lines; one curved line means polarised. Inductor, a series of loops; a bar alongside means a core. Variable anything, an arrow through the symbol. 16 00:03:02.359 --> 00:03:17.313 Transformer, two coils facing each other, usually with core bars between. Diode, triangle pointing into a bar; the bar is the cathode, matching the stripe on the physical part. 17 00:03:17.313 --> 00:03:35.834 LED, a diode with two arrows radiating away. Transistor, a circle with three leads; the arrow's position and direction says which type. Antenna, a stylised whip or a triangle. Battery, alternating long and short lines. 18 00:03:35.834 --> 00:03:49.853 Ground, a descending stack of shortening horizontal lines. Learn these ten and you can read the diagrams without knowing which numbered component the question means. 19 00:03:49.853 --> 00:04:04.020 Naming the blocks. The other half of this material is functional: given a job, name the circuit. Job, Change AC into varying (pulsating) DC; Block, Rectifier. 20 00:04:04.020 --> 00:04:21.146 Job, Control the amount of voltage from a power supply; Block, Regulator. Job, Change 120 V AC to a lower AC voltage; Block, Transformer. Job, An electrically-controlled switch; Block, Relay. 21 00:04:21.146 --> 00:04:38.900 Job, Display an electrical quantity as a numeric value; Block, Meter. Job, A visual indicator; Block, LED. Job, Several semiconductors and other components in one package; Block, Integrated circuit. 22 00:04:38.900 --> 00:04:54.502 Two distinctions the pool leans on: Rectifier versus regulator. A rectifier makes DC out of AC, and what comes out is lumpy, pulsating DC. A regulator holds the level steady. 23 00:04:54.502 --> 00:05:11.718 A power supply usually has both, plus filter capacitors between them, and each does a different job. Transformer versus regulator. A transformer changes AC voltage and cannot change DC at all. 24 00:05:11.718 --> 00:05:21.133 A regulator controls DC output. Confusing them is the most common error in this group. Resonant circuits. 25 00:05:21.133 --> 00:05:28.106 Question. Which of the following is combined with an inductor to make a resonant circuit? 26 00:05:29.006 --> 00:05:31.419 Answer. Capacitor. 27 00:05:32.019 --> 00:05:37.899 Question. Which of the following is a resonant or tuned circuit? 28 00:05:38.799 --> 00:05:44.599 Answer. An inductor and a capacitor in series or parallel. 29 00:05:45.199 --> 00:06:03.089 Straight from the foundations lesson: two opposite reactances that cancel at one frequency. Series or parallel, both are resonant circuits, and they behave oppositely, which is exactly why the answer includes both. 30 00:06:03.089 --> 00:06:04.259 Shielded wire. 31 00:06:04.259 --> 00:06:09.859 Question. Which of the following is a reason to use shielded wire? 32 00:06:10.759 --> 00:06:16.959 Answer. To prevent coupling of unwanted signals to or from the wire. 33 00:06:17.559 --> 00:06:36.494 Note to or from. A shield keeps interference out of a sensitive line and keeps RF in on a transmitting one. In a station both directions matter, and the same cable often needs both. Check yourself. 34 00:06:36.494 --> 00:06:51.199 Your power supply outputs 13.8 V but it sags badly under load. Rectifier or regulator? On a schematic, what does an arrow drawn through a component mean? 35 00:06:51.199 --> 00:06:57.639 What two components make a tuned circuit, and in what arrangements? 36 00:07:03.639 --> 00:07:23.639 The regulator, its job is holding the level steady. A failing rectifier shows as excessive ripple or no output at all. That the component is variable or adjustable. An inductor and a capacitor, in series or parallel.