Resistance

Each component resists the flow of charge carriers through it.Metals are made of a lattice of vibrating positive metal ions surrounded by delocalised electrons. When you apply a potential difference across the metal, electrons flow towards the positive end.Resistance is the ratio of the potential difference across a component to the current through the component.Electrical components called resistors have known resistance. All components have resistance. It takes energy to push electrons through the component and the higher the resistance the more energy it takes.The unit of resistance is the ohm Ω.One ohm is defined as the resistance of a component when the p.d. of 1V produces a current of 1A.