1. TOC 1 Physics 212 and 222 Current and Resistance Current Batteries Basic Circuit Elements

2. TOC 2 Physics 212 and 222 Current and Resistance Current is a measure of the movement of charge

3. TOC 3 Physics 212 and 222 Current and Resistance Current is defined as the amount of charge that passes through a surface in a given amount of time. The units of current are amps The direction of the current is opposite to the flow of electrons. It may be thought of as the flow of positive charge. Current always flows from higher potential to lower potential.

4. TOC 4 Physics 212 and 222 Current and Resistance A battery uses chemical reactions to cause a potential difference between the terminals + - The maximum value of the potential difference of a battery is called its voltage In a circuit diagram we draw it like this - + V

5. TOC 5 Physics 212 and 222 Current and Resistance Zn + 2 OH - —> ZnO + H 2 O + 2 e - 2 MnO 2 + H 2 O + 2 e - —>Mn 2 O 3 + 2 OH - Zn + 2MnO 2 —> ZnO + Mn 2 O 3 + 1.5 V Cathode (MnO 2 ) Anode (Zn) H2OH2O MnO 2 Zn OH - ZnO Mn 2 O 3 This is how an alkaline cell (AA battery) works.

6. TOC 6 Physics 212 and 222 Current and Resistance Current is defined as the amount of charge that passes through a surface in a given amount of time The direction of current is opposite to the flow of electrons The current may be though of as the flow of positive charge Current always flows from higher potential to lower potential In other words, current flows from the positive terminal of the battery through the circuit to the negative terminal In a circuit diagram we draw it like this The units of current are amps (A) - + V I + -

7. TOC 7 Physics 212 and 222 Current and Resistance The following circuit elements and their symbolic representation are the ones most commonly found in circuits. Battery V -+ V NameSymbolUnits Resistor Capacitor Inductor Switch R Ω C F L H S

8. TOC 8 Physics 212 and 222 Current and Resistance Current Batteries Basic Circuit Elements