Castle Electricity Section 3 PDF

**Castle Electricity** **Section 3** Schematic diagrams: - The positive end of the battery is always the longer line and has a + on top. - The negative end of the battery is always the shorter line and has a -- on the bottom. - Continuous flow shows the arrow coming out of the pos...

**Castle Electricity** **Section 3** Schematic diagrams: - The positive end of the battery is always the longer line and has a + on top. - The negative end of the battery is always the shorter line and has a -- on the bottom. - Continuous flow shows the arrow coming out of the positive terminal into the negative terminal. Remember that the compass cannot tell you which is actually occurring. This is "conventional" direction. - **Capacitor:** two layers of conducting material separated by an insulator - The conducting layers are called capacitor plates - The insulating layer prevents movement of charge from one plate to the other inside the capacitor. - The plates have large surface area to store a large amount of charge. The plates are also very thin so it can be rolled into a cylinder. - Each plate has a wire attached to it called a terminal which extends outside the can. - What is inside a capacitor? - - Capacitance: the "charge-holding" ability of a capacitor - Measured in a unit called Farad (F) - How do capacitors work? - A black and white symbols Description automatically generated - Set up the circuit and draw the arrows. - The charge cannot go over the capacitor plates on the schematic. Demonstration time: - Set up a battery with 2 round bulbs. - Charge the capacitor. - See the time it takes to charge and discharge the circuit. - Time: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ - Set up a battery with 2 round bulbs. - Charge the capacitor again and note the time. - Time: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ - Replace the 2 round bulbs with 2 long bulbs. - Discharge the capacitor with the 2 long bulbs and note the time. - Time: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ - Set up a battery with 2 long bulbs - Charge the capacitor and note the time. - Time: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ - Replace the 2 long bulbs with 2 round bulbs. - Discharge the capacitor with the 2 round bulbs and note the time. - Time: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ - Talk about resistance and flow rate. - Long bulb = \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ resistance - Short bulb = \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ resistance The Genecon - The Genecon only pumps charge while storing nothing. - The battery pumps charge and "stores" energy. Air capacitor: - Demonstration with the "air capacitor" - Blow air into the capacitor. What do you see? - Suck air into the capacitor. What do you see? - Put a finger over the capacitor after you blew into the other end. What do you see? - Just as a capacitor cannot have electrons "jump" between the insulator the balloon acts as an insulator to the 2 sides of air movement. Air is already present in both sides. - A friend argues that the air capacitor is not really like the electric capacitor because movement of the balloon is what drives air out during charging. The friend points out that there is nothing moving in the electric capacitor which could drive charge out during charging. How could you counter this argument? - Recall that a person can inhale air out of one of the jars of the air capacitor. In this case, movement of the balloon is an effect of air depletion --- rather than the cause. - Using the analogy of the air capacitor, what do you think might be making charge move during capacitor discharging? - A compressed spring expands, and air compressed in a balloon spontaneously expands when the balloon bursts. Students may suggest that one plate is full of compressed charge, that one plate is at a higher pressure, or that the charge has been squeezed into one plate. Moveable charge is present in all conducting matter. - Benjamin Franklin (1706-1790) came to the same conclusions when he did his pioneering work in electricity a few years before the American Revolution. Franklin is the person who first used (+) and (-) symbols in electricity. However, he did not mean them in the sense of the modern explanation. - (+) represents a MORE-THAN-NORMAL amount of charge ("extra" charge) - (--) represents a LESS-THAN-NORMAL amount of charge ("missing" charge) Energy is best defined as an invisible entity that can be stored in matter and transferred to other matter \-- and is what gives matter the ability to make something happen. In most of the circuits we have observed, the source of the stored energy has been the battery. In some circuits, however, there was no battery present. in circuits where a Genecon was used, the source of energy was not the Genecon itself; the source of energy was the person doing the cranking. The cranking action transferred the energy stored in your muscles to moving charges and lit bulbs. Energy leaves the energy source where it is stored and travels one-way to a receiver. Energy can leave a circuit as heat or light energy from the bulbs (the receivers of the energy). The energy source might be the stored energy in a battery, or the stored energy in muscles used to crank a Genecon, or other energy sources. Energy is transferred from one type to the next (electrical energy to thermal energy) but energy is always conserved.