1. Circuits and Circuit Elements
Schematic Diagrams and Circuits

2. Schematic Diagrams and Circuits
Schematic diagram – a representation of a circuit that uses lines to represent wire and different symbols to represent components
Also called circuit diagrams

3. Electric Circuits

4. Electric Circuits

5. Electric Circuits
Electric circuit – a set of electrical components connected sbuch that they provide one or more complete paths for the movement of charges
Charges move from the battery through a path back to the battery
Load – any element or group of elements that dissipate energy
Needs a source of potential difference and electrical energy (battery) and a load (bulb)
Circuits can be either open or closed
Closed circuit – has a pathway through the circuit from one positive terminal of the battery to the negative
Open circuit – does not have such a pathway

6. Electric Circuits
Overloaded – condition when electrical wires carry more than a safe level of current
Short circuit – accidental creation of an alternative pathway
Reduces the resistance in the circuit
Increases the current

7. Electric Circuits Short circuits Leads to overload
Occurs when a circuit does not have a load (no resistance)
Wires cannot hold that much current, and their insulation may melt or catch on fire
Grounding is used to prevent electric shock from short circuits

8. Electric Circuits
Circuit breaker – a device that protects a circuit from current overloads
Trip when the current overloads
Acts like a switch

9. Electric Circuits
The source of potential difference and electrical energy is the circuit’s emf or electromotive force
Emf - Energy per unit charge supplied by a source of electric current
Batteries and generators
Terminal voltage is less than the emf
Battery acts as both an emf and a resistor, although we will ignore internal resistance of the battery

10. Electric Circuits Emf is not a true force
Potential difference
Voltage rating on a battery (1.5 V)
Terminal Voltage = emf – current * resistance
ΔV = ε - IR

11. Electric Circuits
Potential difference across a load equals terminal voltage
As charges move from one terminal to the other, the chemical energy of the battery is converted into the electrical potential energy of the charges
As charges move through a circuit, their electrical potential energy is converted to other forms of energy (kinetic, thermal, light)
Energy in a circuit must be conserved, so the energy gained in the battery must be equal to the energy lost in the load
Therefore, the potential increase across the battery must equal the potential decrease of the load