Edexcel IGCSE Biology: Double Science 复习笔记 1.1.3 Living Organisms: Excretion Excretion Chemical reactions that take place inside living cells are described as metabolic reactions ...
Edexcel IGCSE Biology: Double Science 复习笔记 1.1.2 Living Organisms: Nutrition & Respiration Nutrition Organisms must obtain food to provide energy Energy is necessary to carry out life proce...
Resistance in a Light-Dependent Resistor A light-dependent resistor (LDR) is a non-ohmic conductor and sensory resistor Its resistance automatically changes depending on the light energy falling on...
Edexcel IGCSE Biology: Double Science 复习笔记 1.1.1 The Unifying Characteristics of Living Organisms The Unifying Characteristics of Living Organisms In order for something to be considered...
Resistivity All materials have some resistance to the flow of charge As free electrons move through a metal wire, they collide with ions which get in their way As a result, they transfer some, or a...
Resistance in a Filament Lamp The I-V graph for a filament lamp shows the current increasing at a proportionally slower rate than the potential difference I-V characteristics for a filament lamp Th...
I–V Characteristics As the potential difference (voltage) across a component is increased, the current also increases (by Ohm’s law) The precise relationship between voltage and current is differen...
Ohm's Law Ohm’s law states that for a conductor at a constant temperature, the current through it is proportional to the potential difference across it Constant temperature implies constant resista...
Defining Resistance Resistance is defined as the opposition to current For a given potential difference: The higher the resistance the lower the current Wires are often made from copper because cop...
Calculating Electrical Power In “Work, Energy and Power”, Power P was defined as the rate of doing work Potential difference is the work done per unit charge Current is the rate of flow of charge S...
Defining Potential Difference A cell makes one end of the circuit positive and the other negative. This sets up a potential difference (d) across the circuit The potential difference across a compo...
Calculating Electric Charge Current can also be defined as the charge passing through a circuit per unit time Electric charge is measured in units of coulombs (C) Charge, current and time are relat...
