HONORS

Circuits Circuit: closed path through which electrons can flow. Two kinds: Series: current has only one path to travel through Ex. Flashlight, holiday lights Parallel: contains more than one path for current to travel through. Ex. House, school Make sure to point out in these pictures the battery, light bulbs, wire/conductor, and the switch. Note in both of these pictures that the switch is closed, therefore the light bulbs are on.

Series vs. Parallel Series: Parallel: One branch/path Simpler All components must work at same time. More items increases the overall resistance. Voltage decreases as it travels through the circuit. Current same throughout. Parallel: Multiple branches/paths More complex Can use one component at a time. More items decreases the resistance. Voltage stays the same throughout. Current split among each pathway.

Series vs. Parallel Some circuits can be a combination, both series and parallel. These two light bulbs are connected in series. These two light bulbs are connected in parallel.

Series and parallel circuit Drawing Circuits Basic notation to know: Parallel circuit (3 pathways) Series circuit (1 pathway) Series and parallel circuit I like to show this first to give them a general idea of how to even get started with drawing. I always tell them to just draw a rectangle for a series circuit. Parallel add more branches to that rectangle. I won’t have CP ever draw a combo circuit, and for honors it would only be bonus.

Drawing Circuits Basic notation to know: Switches Battery Resistor (closed) (open) (one) (two) Resistor Light bulb Ammeter Measures amount of current (Only in series circuits) Voltmeter Measures the voltage drop (Only in parallel circuits) or or

Example #1 Draw a series circuit with a battery, two light bulbs, one resistor, and an open switch. Note: order doesn’t matter on a series circuit!

Example #2 Draw a parallel circuit with two batteries, two light bulbs (on separate branches), a voltmeter on one of the branches, and a switch that could turn off the whole circuit.

Practice Time Draw a series circuit with two batteries, a light bulb, an ammeter, and a closed switch. Draw a parallel circuit with two batteries, 3 light bulbs, 1 resistor, and 3 switches. Each light should be able to be turned off individually.

Overheating If too much voltage is applied to a circuit that can’t handle it, overheating can occur. Two ways to prevent: Fuse: small piece of metal within that melts when overheated to open the circuit and prevent current from flowing. Circuit breaker: piece of metal that bends when overheated to open the circuit and prevent current from flowing.

Calculating Resistance Series: simply add up all resistances to find total resistance. Rt = R1 + R2 + R3…. Parallel: find a common denominator, add them up, then cross multiply and solve for total resistance. 1 = 1 + 1 + 1…. Rt R1 R2 R3

Find the total resistance of this series circuit. Example #3 Find the total resistance of this series circuit. 2 Ω 5 Ω Rt = 2 + 5 Rt = 7 Ω

Find the total resistance in this parallel circuit. Example #4 Find the total resistance in this parallel circuit. 2 Ω 5 Ω 1 = 1 + 1 Rt 2 5 Write it out. Find a common denominator. Add the fractions. Cross multiply. Divide and sovle for Rt. 5 2 1 = 7 . Rt 10 Rt = 1.43 Ω 1 = 5 + 2 . Rt 10 10 10 = 7Rt 7 7