AS AQA Phys Unit 1- E.M.F and Internal Resistance

Resistance and batteries

Resistance comes from electrons colliding with atoms and loosing energy. In a battery, chemical energy is used to make the electrons move. As they move, they collide with atoms inside the battery -so batteries must have resistance. This is called internal resistance.

Internal resistance of a source of electricity is due to the opposition of flow of charge through the source. This causes electrical energy produced by the source to be dissipated inside the source when charge flows through it. It is defined as the loss of potential difference per unit current in the source when current passes through the source.

Internal resistance causes batteries and cells to warm up when they're used. Chemical reactions in the battery produce electrical energy. The amount of electrical energy the battery (or source) produces for each coulomb of charge (unit charge) is called its electromotive force (emf). Emf isn't actually a force and is measured in volts.

Load resistance is the total resistance of all the components in the external circuit. It is also known as external resistance. The potential difference across the load resistance (R) is the energy transferred when one coulomb of charge flows through the load resistance. The potential difference is called the terminal p.d. (V). If there was no internal resistance, the terminal p.d. would be the same as emf. However, in real power supplies, there's always some energy lost overcoming the internal resistance. The…