Lesson Notes By Weeks and Term v4 - JHS 3
ELECTRICITY AND ELECTRONICS
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ELECTRICITY AND ELECTRONICS
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Science
Class: JHS 3
Term: 2nd Term
Week: 10
Grade code: B9.4.2.2.1
Strand code: 4
Sub-strand code: 2
Content standard code: B9.4.2.2
Indicator code: B9.4.2.2.1
Theme: FORCES AND ENERGY
Subtheme: ELECTRICITY AND ELECTRONICS
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In many devices used in Ghana—phone chargers, radios, TV sets, solar lamps, traffic lights, and even some irrigation controllers—diodes and LEDs are used to control the direction of current. Understanding forward bias and reverse bias helps learners to know why an LED lights in one direction but not in the other, and how simple electronic circuits are built safely (e.g., using resistors to prevent burning an LED).
2.1 What is a diode and an LED? A diode is an electronic component that allows electric current to flow mainly in one direction and blocks it in the opposite direction. An LED (Light Emitting Diode) is a diode that emits light when current passes through it in the correct direction.
Important LED parts/labels Anode (+): the side that should be connected to the positive terminal during forward bias. Cathode (−): the side that should be connected to the negative terminal during forward bias.
How to identify anode and cathode on a typical LED The longer leg is usually the anode (+). The shorter leg is usually the cathode (−). The LED body often has a flat side near the cathode (−). 2.2 What does “bias” mean? Bias means applying a voltage across a diode in a particular direction to make it either: conduct (allow current), or block current.
So, forward bias and reverse bias describe *how the battery is connected to the diode*.