13 April 2015 6.5 Electrical Energy and Charge How many meanings of the word charge can you think of? 6.5 Electrical Energy and Charge 13 April 2015 Page 192 AQA Physics • What is electric current? • What is the unit of electric charge? • What energy changes take place when charge flows through a resistor? What is electric current? Conventional current electrons Conventional current In metals current is a flow of electrons. In all materials current is a flow of charged particles. What is the unit of charge? • Charge is measured in Coulombs, C. • Charge flow = current x time (Coulombs) (Amperes) (seconds) E.g. A flow of 2A for 5s is a charge of 10 Coulombs. Page 192 Q a) The capacity store of a battery is shown as Amp-hours or milliamp-hours (mAh). This tells you how long a battery can deliver a certain current. Energy and potential difference Energy transformed = potential difference x charge flow From page 193 copy the worked example and answer b). Summary • An electric current is a flow of charge. • When charge flows through a resistor, electrical energy is transferred as heat. • Charge = Current x time • Energy transferred = pd x time