An electric circuit is a closed path that allows electrons to flow from an energy source and back. A closed circuit allows continuous electron flow, while an open circuit interrupts flow. Common circuit components include batteries, wires, switches, bulbs and resistors. Circuit diagrams use symbols to represent components and visualize connections before building real circuits. Series circuits have a single current path, so adding resistors increases total resistance and dims all bulbs. Parallel circuits provide multiple paths, so adding resistors decreases total resistance despite each path's resistance increasing.

1. CIRCUITS

2. Electric Circuits An electric circuit is a closed path along which electrons can flow from and return to an energy source

3. Electric Circuits The two locations in a cell that must be connected to other components are the positive terminal and the negative terminal .

4. Electric Circuits A closed circuit is a complete electric circuit that allows electrons to flow along an uninterrupted path

5. Electric Circuits Electrons do not flow through any part of a circuit where there is a gap or break . An open circuit is one in which there is an opening that does not allow current to flow

6. Electric Circuits For example, if a bulb is loose and does not make contact with the base of its socket, the circuit is open and the bulb will not glow .

7. Electric Circuits A break in the filament of an incandescent bulb also creates an open circuit. (This is the most common reason why a bulb doesn’t glow)

8. Electric Circuits A switch is a control device that can complete or break a circuit it is connected to. A switch is not essential for a circuit to operate, but it is usually included for convenience.

9. Circuit Diagrams Engineers and designers of electrical circuits use special symbols that show the components and connections in a circuit. These symbols make it easier to plan and analyze a circuit before you build it A drawing made with these symbols is called a circuit diagram .

10. Circuit Diagrams Symbol: Component: wire Function: conductor allows electrons to flow

11. Symbol: Component: cell, battery Function: electrical source longer side is the positive terminal, shorter side is the negative terminal Circuit Diagrams

12. Symbol: Component: lamp (light bulb) Function: load converts electricity to light and heat Circuit Diagrams

13. Symbol: Component: general resistor/load Function: general load converts electricity to heat Circuit Diagrams

14. Symbol: Component: switch Function: opens and closes the circuit Circuit Diagrams open switch closed switch

15. Symbol: Component: ammeter Function: measures current through a device connected in series Circuit Diagrams

16. Symbol: Component: voltmeter Function: measures voltage across a device connected in parallel Circuit Diagrams

17. A series circuit is an electric circuit that has only one path along which electrons can flow. If that pathway is interrupted , the whole circuit cannot function Series Circuits

18. The amount of current is the same in all parts of a series circuit. However, if you add more resistors you increase the total resistance of the circuit. Series Circuits

19. For example, adding an extra bulb to a series of lights makes all of the bulbs dimmer Series Circuits

20. In a parallel circuit, each component has its own path for current . The points where a circuit divides into different paths are culled junction points . Parallel Circuits

21. An interruption or break in one pathway does not affect the other pathways in the circuit.

22. Adding a new pathway with more resistors does not affect the resistance of any of the other pathways. In fact, adding extra resistors in parallel decreases the total resistance of the circuit. Parallel Circuits

23. This might seem counterintuitive, but think about how much less resistance there is when you drink with two straws instead of one Parallel Circuits

24. Summary Adding resistors in parallel decreases the total resistance of the circuit The current divides into different paths Each load uses all the potential difference supplied by the battery Parallel The current decreases when more resistors are added The current is the same throughout the series circuit Each load uses a portion of the total potential difference supplid by the battery Series Resistance Current Potential Difference Circuit