Campbell Science



Circuits Lab – Week 33.1 – Drawing CircuitsMany of the circuit diagrams in earlier sections sketched the “visual” appearance of circuits — drawing batteries, bulbs, and wires as they actually appear. From now on we will draw “schematic” diagrams — using symbols to represent the circuit components. The battery symbols used in this manual from now on are shown below.The positive terminal of the battery is represented by a long, thin line and a + sign. The negative terminal of the battery is represented by a short, thick line with a – sign.Additional schematic diagram symbols are shown below.Note the difference between the visual circuit on the left and its schematic diagram on the right.In the space to the right of the visual circuits, draw the schematic diagram for the circuits.3.2 – Electric PressureLook at the syringe circuit at the front of the room. Try to compress one side and watch what happens to the other. Try to compress one side while holding the other side still.What happens to the air pressure inside the syringe as you decrease the volume?Do you think the air is trying to expand back out when you compress it? What evidence do you have?A battery is a device that has electric pressure, much like the syringe being squeezed has air pressure. Inside a battery there is a chemical reaction that separates a substance into its ions. One side of the battery has a high electric pressure (the positive terminal) and one side of the battery has low electric pressure (the negative terminal). The pressures don’t equalize inside the battery because the chemical reaction prevents it. But when the battery is connected to a circuit, the difference in electric pressures causes charge to flow from an area of high pressure to an area of low pressure.Electric pressure is given the name voltage and is measured in volts.3.3 – Color CodingColors can be used to represent electric pressure values in circuits. Color-coding a circuit enables you to visualize pressure differences. It will help you to see which light bulbs light and their relative brightness.The following is the color system that will be used:Rules for Color Coding – 1.) The battery maintains the highest pressure difference in a circuit. Color the positive terminal and all the wires connected to it RED. Color the negative terminal and all the wires connected to it BLUE.2.) Use only color for a wire (and all the wires connected to it)3.) Use different colors for each side of a light bulb.4.) Do not color light bulbs.5.) Bulbs of the same brightness will have the same color jump.Why do you think wires are given uniform colors?Practice:Color Code the following circuits. Then put starburts on each lightbulb.3.4 – Different Bulbs in ParallelColor Code the circuit below.Add starbursts to the bulbs based on the color difference across each one.How do you predict the brightness of the bulbs to compare?Now build the circuit. How do the brightness of the bulbs compare?According to the color coding you did earlier, why are the bulbs equally bright?3.5 – Series vs. ParallelFrom Lab 1 you learned that things connected in series have the same charge flow (current) because they have the same compass deflection.From 3.4 you have seen that things connected in parallel have the same pressure difference (voltage) because they have the same color jump.IMPORTANT!!! :Series = Same CurrentParallel = Same VoltageSUMMARY1.) All bulbs are identical. Rank them in order of brightness.2.) All bulbs are identical. Rank them in order of brightness.3.) Things in series have the same ______________________________.4.) Things in parallel have the same _____________________________. ................
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