Principles of Physics

 A circuit with one resistor  When one electron leaves the voltage supply another one enters  How fast this exchange occurs is based on resistance  One electron pushes another and so on

 More than one resistor in a single path  Each electron must go through every resistor  Total resistance increases with every resistor added in series

 Current flow depends on all resistors  Current through each resistor is the same I T = I 1 = I 2 = … R1R1 R2R2

 A voltage exists across every device (voltage supply, resistors, light bulbs, etc.)  As an electron goes through a resistor or device it loses energy because it does work to get through  How much energy lost per Coulomb (voltage) depends on the resistance

 Voltage gained by electrons when leaving the voltage supply equals the total voltage lost before returning  Since voltage is lost through all resistors V T = V 1 + V 2 + … R1R1 R2R2

To determine the current leaving the voltage supply the total resistance must be used R T = R 1 + R 2 +… R1R1 R2R2

Determine the total current in the circuit V = IR 12 V = I(24 Ω ) I = 0.5 A 10 Ω 14 Ω 12 V R T = R 1 + R 2 = 10 Ω + 14 Ω = 24 Ω

Determine the voltage in the 10 Ω resistor V = IR V= 0.5 A(10 Ω ) V = 5 V 10 Ω 14 Ω 12 V

Determine the voltage in the 14 Ω resistor V = IR V= 0.5 A(14 Ω ) V = 7 V 10 Ω 14 Ω 12 V or V T = V 1 + V 2 12 V = 5 V + V 2 V 2 = 7 V

5 Ω 12 V 5 Ω 12 V 5 Ω A B By adding another resistor in series Increase total resistance Decreases current Voltage across each resistor decreases

 Adding a resistor in series increases the total resistance  When one resistor is disconnected the circuit is open – current does not flow  Everyone has to go through all doors to get out  The smallest door slows the movement the most