2c) Energy and Potential Difference in Circuits Part 1 Current and Charge

Current, voltage, charge, circuits??? Think in terms of energy In a complete circuit charges gain energy from the power supply and then they transfer this energy to any components in the circuit. They then return to the power supply that transfers energy to them again.

Charge Q Negatively charged electrons In a wire the electrons move about randomly. Once a cell or battery is attached to the ends, some of the electrons (charges) will start to flow to the positive terminal

Charge (Q) In a good conductor, such as a copper wire, these charges move towards the positive terminal when a cell or battery is connected. This is called an electric current One electron carries only a tiny amount of charge so we measure charge in larger units called coulombs (C) (one coulomb is the charge carried by 6x10 18 electrons) 6x100,000,000,000,000,000

Current, I Current is the ‘rate of flow of charge’. Current (I) is measured in amps (A) A flow of 1 amp means that 1 coulomb of charge passes by each second so: 1 amp = 1 coulomb per second 1A = 1 C/s Current is measured with an Ammeter

To calculate the amount of charge (Q) that flows we use the equation: Charge = current x time

Question 1 Calculate the total charge that flows through a wire in 10s if the current is 4A.

Question 2 Calculate the current if 20 C of charge pass in 4 seconds.