[PHY] Chapter 17 - Current Electricity

DARRELL ER (COPYRIGHTED) © TOPIC 17: CURRENT ELECTRICITY DARRELL ER (COPYRIGHTED) ©

CHAPTER ANALYSIS THE ABOUT TIME EXAM WEIGHTAGE DARRELL ER (COPYRIGHTED) ©

CURRENT CHARGE / TIME CONVENTIONAL CURRENT & ELECTRON FLOW KEY CONCEPT DARRELL ER (COPYRIGHTED) ©

visualising electricity CHARGE CURRENT VOLTAGE DARRELL ER (COPYRIGHTED) ©

PIKACHU RACE VISUALISATION This is a story about a pikachu participating in a race. He has to run one full lap around the circuit. He starts off at the Pokemon center with full health. However, along the way, he come across Team Rocket. Although Team Rocket offered some resistance, Pikachu was still able to defeat them as usual. He uses all his energy and thunderbolt the shit out of them. Now he is out of energy but with nothing left in his way, he makes his way safely back to the Pokemon center and replenishes his energy back to full health. Pikachu is ready to go again! DARRELL ER (COPYRIGHTED) ©

COMPLETE CIRCUIT VISUALISATION This is how electricity works! Pikachu is the charge, a particle capable of carrying electrical energy, that moves around the circuit. Pokemon center is the source (battery), where the charge replenishes its electrical energy after going one round around the complete circuit. In the battery, chemical potential energy is converted to electrical energy which is supplied to the charge. Team Rocket is the component (light bulb). In order to overcome it, the charge has to use its electrical energy. After the charge hands over the required electrical energy, it is then allowed to pass through. In the light bulb, electricity energy received from the charge is converted to light and heat energy. charge component battery DARRELL ER (COPYRIGHTED) ©

CURRENT VISUALISATION SO WHAT IS CURRENT? Current is defined as the rate of flow of electrical charges. In order words, the amount of charges flowing in the circuit per second. VISUALISATION The whole process of pikachu going around the circuit is really quick, in milliseconds. Furthermore, multiple pikachus can be released to go around the circuit at the same time. Current measures the number of pikachus going around the circuit every second! Another analogy is ERP. The amount of cars passing through the ERP per second, is the rate of flow of cars. Current is the rate of flow of charges! charge component battery DARRELL ER (COPYRIGHTED) ©

DEFINITION Current is defined as the rate of flow of electrical charges. Unit: Ampere (A) Formula: Current is measured with an ammeter (which has very low internal resistance). The low resistance is to ensure that the ammeter does not affect the current flow. It must be connected in series so that electric current flow through the ammeter, via the positive terminal and leave via the negative terminal. (It’s like a ERP, cars must go through it!) CURRENT Conventional current flows from positive to negative terminal. Electron flow is from negative to positive terminal. DARRELL ER (COPYRIGHTED) © Convectional Current Electron Flow Current = Charge Time

VOLTAGE ELECTROMOTIVE FORCE POTENTIAL DIFFERENCE KEY CONCEPT DARRELL ER (COPYRIGHTED) ©

A COMPLETE CIRCUIT VISUALISATION Electromotive Force The amount of electrical energy the battery provides to each charge depends on the amount of components in the circuit. So if there are 3 light bulbs, the battery must provide sufficient energy to the charge to go past all the components and be able to complete a full circuit. This is also known as electromotive force, referring to how much energy the source provides to each charge. Potential Difference Before the charge enters the component, it will possess a certain amount of electrical energy. After it passes through it, it will have a lesser amount of energy. The difference between before and after is known as potential difference, referring to how much electrical energy is consumed per charge by the component. Both emf & P.D have the same formula, emf = Work Done / Charge P.D = Work Done / Charge But I prefer to remember it as, Voltage = Energy per Charge charge component battery component component DARRELL ER (COPYRIGHTED) ©