Pageof 7Physics Lab (Online Simulation) 1 CAPACITOR AND CAPACITANCE Electricity and Light TA name: Due Date: Student Name: Student ID: This lab uses the Capacitor Lab: Basics simulation from PhET Inte

Pageof 7Physics Lab (Online Simulation)1CAPACITOR AND CAPACITANCEElectricity and LightTA name: Due Date:Student Name:Student ID:This lab uses the Capacitor Lab: Basics simulation from PhET Interactive Simulationsat University of Colorado Boulder, under the CC-BY 4.0 license, and designed for OnlineLabs. Goals:Students will be able to:● Identify the variables that affect the capacitance and how each affects the capacitance.● Determine the relationships between charge, voltage, and stored energy for a capacitor.● Relate the design of the capacitor system to its ability to store energy.● Explain how to use a capacitor to light a bulb.● Describe what happens as charge drains away from a capacitor into a light bulbTheory:A device that can store charge and hence store energy, as potential energy, in an electricfield is called a capacitor. The basic elements for any capacitor are two (or more) isolatedconductors carrying equal but opposite charges, Q. Regardless of the geometry of twoconductors, they are called “plates” and are easiest to visualize as two parallel plates asshown below.Figure 17-1In such a configuration, the electric field between the plates (ideally) is just V/d where V isthe potential difference and d is the plate-separation. Since the electric field E isproportional to the charge density and hence to the total charge Q (from Gauss’ Law), itcan be stated that,Q VThe constant of proportionally is defined as the capacitance of a specific device.+ + + + + + + + + +_ _ _ _ _ _ _ _ _ _Physics Lab (Online Simulation)2Q = CV.Note that, C is a derived unit which is coulombs/volt. This unit is called the farad (F).Combination of CapacitorsWhen two or more capacitors are combined in either parallel or series (see drawing below) theyform a new equivalent capacitor Ceqv. Capacitors in parallel will form a new capacitance whosevalue is the sum of the individual capacitors connected in parallel (Equation [1]). Capacitors inseries will form a new capacitance whose value is the inverse of the sum of the inverses of eachindividual capacitor connected in series (Equation 2)Parallel n321eqv CCCCC  [1]Series n321eqv C1C1C1C1C1  [2]Note: When capacitors are connected in series the new equivalentcapacitance will be less than the smallest capacitor.Capacitors, which are usually available only in a small variety of fixed values, may becombined to create a desired capacitance using the two methods above or a combination of thetwo.Capacitors in parallelCeqvCapacitors in SeriesCeqvPhysics Lab (Online Simulation)3This pre-lab is worth 5 points.TYPE ALL YOUR ANSWERS IN BLUE1) What physical parameters does Capacitance depend? (check out the formula in the book)2) The unit for capacitance is called a ________________________and it is designated byletter________.3) A graph of charge (q) vs. volts (V) should yield a linear line with the slope representing whatquantity?4) Identify and write the equation for the two circuits shown below to determine the total equivalentcapacitance.5) Determine an equation to find the equivalent capacitance of the circuit by combining theequations above.Physics Lab (Online Simulation)4Develop your understanding: Open the Capacitance screen, then explore to develop yourown ideas about how a capacitor is designed.Explain your understanding: Use your own words and captured images from the simulationto:1. Identify what features of a capacitor can be maximized or minimized to make a capacitorwith the greatest capacitance.a. What features of the simulation did you use to help you?2. Design experiments to find the relationships between charge, voltage, and stored energyfor a capacitor. Summarize your experimental procedures and findings. Note* the formulafor stored energy of a capacitor is U = ½ * QV = ½ * C 2From C = Q/V, we can show that capacitance only relies on the geometry of the capacitor.Therefore, C should remain constant if we fixed the distance and area of the plates and varythe voltage. Simultaneously, we should see that the stored energy increases as the voltageincreases.Ensure that capacitance, top plate charge, and stored energy are turned on.1) Minimize the plate area and maximize the plate distance of the capacitor2) Attach the probes of the voltmeter to each side of the battery to monitor the voltage.3) Set the voltage to zero. Record the voltage, charge, capacitance and energy. Repeat fordifferent values of V.Physics Lab (Online Simulation)5Table 1Voltage (V) Charge (pC) Capacitance (pF) Energy (pJ)00.1500.2500.5001.0001.500What did you observe about the capacitance and stored energy?1) Adjust the battery to 1.5 V2) Minimize the plate area and maximize the plate distance of the capacitor.3) Record charge, capacitance and energy for varying separation distances.Table 2Distance (mm) Charge (pC) Capacitance (pF) Energy (pJ)10952Now minimize the separation distance and plate area. Complete table 3.Table 3Area (mm) Charge (pC) Capacitance (pF) Energy (pJ)1002003004003. If you wanted to design a capacitor system to store the greatest energy, what would youuse?Physics Lab (Online Simulation)6Develop your understanding: Explore the Light Bulb screen to investigate how to use acapacitor to turn on a light bulb.Explain your understanding: Use your own words and captured images from the simulationto show you know how to use a capacitor to light a bulb.Now that we know how to maximize and minimize the energy of a capacitor let’s see how itdissipates the stored energy through a lightbulb. Using a constant 1.5 V from the battery adjustthe area and distance so that the capacitor has the least amount of stored energy. Turn the switchto the battery to charge the capacitor. Now flip the switch to discharge the capacitor through thelightbulb. Now adjust the capacitor to have the most amount of stored energy and repeat theprocess. What did you observe?4. What are the required components to use a capacitor to light a bulb and how does thesystem operate?Physics Lab (Online Simulation)75. How would using a capacitor to light a bulb compare to using just a battery as shown:a. Use Circuit Construction Kit Intro screen to test your ideas and providesupporting evidence.6. Describe what happens as charge drains away from a capacitor into a light bulb. Whathappens to the stored energy? Include the use of as many tools in the simulation aspossible in your observations. Note* there is no capacitor in the construction kit. You willhave to use your understanding from both the lightbulb simulation and the constructionkit simulation. Notice that in the construction kit we can change the charge convention.The convention is that “current” flows from positive to negative, however the “electrons”are flowing from negative to positive.7. Research to find a practical application where the energy stored in a capacitor is used.