1. Electric Circuits
Chapter 35

2. Circuit
Complete path from a positive to negative terminal of a battery
Electrons flow from the negative to positive end

3. Parts of a circuit Battery Closed switch (allows electrons to flow)
Open switch (impedes flow)
Wire
Resistor
Light Bulb

4. Types of circuits
Depend on how more than one device receive electrical energy
Series
Single pathway of electron flow
Parallel
Branched pathway, each of which is separate path for the flow of electrons

5. Series Circuits Properties
Only one path for electric current to flow
The amount of current passing through each device is the same
Current is resisted by all three devices in series, therefore, the total resistance equals the resistance of each device
RT=R1 + R2 + R3

6. Ohm’s Law applies to the overall circuit
I = V/RT
Ohm’s Law applies to each individual device on the circuit
Objects with greater resistance, need higher voltage (more energy) to move the same amount of current
Total voltage across the circuit equals the sum of the voltages across each individual device
VT = V1 + V2 + V3

7. Disadvantages of Series Circuits
If one device fails, it causes an open circuit where no current can flow

8. Properties of Parallel Circuits
Each device has its own path of current flow
The current in one device does not pass through the others
Each device connects to the same two points on a circuit, so voltage is the same across both devices
Total current divides among the parallel branches
Current passes more easily into devices with low resistance, so current is inversely proportional to the resistance of that branch
Ohm’s law applies separately to each branch

9. Total current equals the sum of each parallel branches current
IT=I1 + I2 + I3
As number of parallel branches increases, the overall resistance decreases
Overall resistance of the circuit is less than the resistance of any one of the parallel branches
1/RT = 1/R1 + 1/R2 + 1/R3