Name:______Date:______Per:______
Solar Cell Power: Series or Parallel?
Materials: (per group)
2 Solar panel units (2 solar cells)
Desk lamp (light source)
Sets of leads (black & red)
Load (LED light, motor w/fan blade, holiday lights, incandescent light source, etc.)
Ruler
Optional:
Color filters (ex: red, blue, green)
Solar panel covers (tissue, white paper, clear plastic, black paper)
Multimeter
Calculator
Safety notes: Desk lamps can get very hot, so take care when moving them. Color filters should be kept far enough away from light to not melt. Teacher may reduce lighting in classroom to maximize results collected & observed—move around room carefully. If using the motor/fan, be careful not to injure yourself since high rpms can be achieved. If you are unsure how to set up your circuit throughout the lab, ask your teacher about your arrangement so you don’t burn out a bulb or motor.
Directions:
Simple Circuit to Load
A simple circuit includes the power source (solar panels/cells), conductors to carry electricity (wires), and a load (motor/lights).
1. Connect wires from solar to load. Aim at the lamp and observe. Change the angle of the solar panel to the lamp. What angle seems to work best for the load?
2. Notice which way the motor spins. Switch connections to the load and observe. What happens when you switch them (reverse polarity)?
Series Circuit to Load
Series wiring connects PV cells in a chain, from positive (+) to negative (-) between each panel. The electrons follow one path.
3. Connect the black (-) wire of one solar panel to the red (+) of another cell. Connect the remaining wire from each panel to the load wires. Is the load different than it was in the simple circuit? Explain.
4. What happens when you shade one panel? Why do you think this happens in a series circuit?
Parallel Circuit to Load
When PV cells are wired in parallel, the positives (+) of each panel are connected to one side of the load, and the negatives (-) of each panel are connect to the other. This gives two paths for the current to follow through the load. Parallel circuits are often used to power loads on a cloudy day.
5. Connect the red wires from two solar panels onto one load wire. Connect the black wires from the panels onto the other load wire. Is the load different compared to the simple & series circuits? Explain.
6. What happens when you shade one panel? Why do you think this happens in a parallel circuit?
Now that you have made all the circuits, conduct additional investigations according to your teacher’s directions. You may now be using a multimeter & Ohm’s law.
Explore the effects of-
· Moving the lamp closer & further away
· Partially covering and uncovering the solar panel(s) with one or multiple materials
· Tilting the panel(s) backwards and forwards
· Using different colored light filters
7. For your new experiment, you must write a hypothesis, list you independent & dependent variables, controls, and construct a data table for results, calculations (if applicable), & observations. Also include a procedure that explains what you did. Attach your information by stapling to this sheet.
Analysis & Conclusion:
8. Summarize all of your results. Include appropriate electrical terminology.
9. Explain any possible sources of error or any problems/issues during the experiment(s).
10. How do your results relate to real conditions with the Sun? Explain your answer.
11. Explain how your results could apply to someone using solar energy to generate electricity.
Series and Parallel Circuits Basics Name:
Directions:
1. Log on to your computer.
2. Go to the following website: http://phet.colorado.edu/index.php
3. Click the button “Play with sims…”
4. Click on the Physics category on the left, then the application that says Circuit Construction Kit (DC only).
5. Click “Run now.”
You now have the raw material to create a circuit. Take a moment to look over the site and find all the different materials. To build a circuit you will need several wires, a light bulb, a voltage source, a voltmeter, and a non – contact ammeter. Play with it to see how to grab and manipulate these tools.
Click the reset button.
A. Series Circuits
Build a simple series circuit that consists of 6 pieces of wire, 1 light bulb, and 1 battery (voltage source). In order to complete the circuit, the red circles at the end of each must overlap. Please note that the light bulb also has TWO circles. Your circuit is complete and working when the light comes on and the blue dots begin moving. Draw a picture of your circuit here:
What do you think that the moving blue dots represent?
Use the tools at the side to get a voltmeter and a Non-contact ammeter. Put the voltmeter near the battery and place the red tab at one end and the black at the other.
What is the voltage? ______
Place the ammeter crosshairs over the moving blue dots. What is the reading? ______
What does this tell us about the circuit?
Use the left button to play with the resistance and voltage of the battery. Make observations on how this changes the readings on the voltmeter and ammeter. Record your observations below. Be sure to record the changes you made and then the effects.
Click the advanced tab and alter the resistivity of the wire. Record your observations:
B. Parallel Circuits Click the reset button to begin working on a parallel circuit. Parallel circuits provide more than one path for electrons to move.
Sketch below a parallel circuit that includes 10 wires, 2 light bulbs and 1 voltage source:
Create this using the simulator tool. The blue dots will be moving and both lights will be on once the circuit is complete. Use the voltmeter and non-contact ammeter to measure electron flow and push.
Voltage:______Ammeter:______
How does this compare with your observations in the series circuit? Is this surprising? WHY or WHY NOT?
Alter resistance and voltage and record your observations below:
Now right click on one of the wires connected to a light bulb. Remove the wire and record your observations:
Does this affect the voltage, amperes, or visually change the appearance of the light bulb?
Replace the wire. Now remove one of the wires touching the voltage source. What happened?
What is the difference between removing the first wire and the second? Why is this significant?
C. Comparisons
Create a second series circuit and record your observations about the two once they are side by side.
You may use the tool to play around. Create a circuit using a switch. Diagram your circuit below and record observations:
Energy, Electrical Components, Circuits, and Terminology Background Information:
What is Voltage?
Voltage is to electricity as pressure is to water; both are forces that move things.
Voltage is the force that moves electrons through a circuit; the greater the voltage the greater the force of electron movement. Voltage is generated by creating a “potential difference” between positive and negative elements of the device generating it.
Like water, the higher the voltage, the more force it exerts. Water falling from a height uses gravity to create force; the higher the water falls (its potential difference), the more force or pressure it creates. Unlike water, however, voltage is not created by gravity but by chemical, optical, or magnetic forces.
Batteries use chemicals to generate voltage while common fuel cells use electrons in hydrogen gas to create voltage. Solar panels use optical means to capture the sun’s photons to do the same and wind turbines use rotating magnets that are very close to coils of wire that generate voltage based on the magnetic fields created by the magnet’s rotation.
Voltage is measured in units called volts
What is Current?
Electrical current is to electricity as the volume of water is to water flow. A fire hose can carry more water at higher pressure compared with a clogged showerhead. So too can lager wires carry more current as compared with smaller wires.
Electrical current carries electrons along a path (called a circuit) like water carries water molecules through a hose. More electrons mean more current flow.
Water normally flows from upstream to downstream using gravity as a force. Electrical current normally flows from positive (+) to negative (-), which is called direct current or DC for short, but gravity is not involved.
Unlike water, electrical current can flow in either direction – positive to negative and negative to positive. The latter is usually called alternating current, or AC, since the current switches (alternates) between positive and negative directions. Electrical current produced by batteries are DC while electrical current coming out of the wall socket is AC. Both have their applications in electronic circuits.
Current is measured in units called amperes or amps
What is a Power Source?
An electrical power source is a device that produces electrical voltage and current and power. Power sources can use chemical energy like a battery or fuel cell, solar energy like a solar panel or wind energy coupled with magnetic energy such as a wind turbine. Each of these power sources converts one kind of energy (chemical, light or mechanical) to electrical energy.
The equation for electrical power is shown below:
P = V * I where
P = Power in watts
V = Voltage in volts
I = Current in amps
What is a Circuit?
A circuit is any “unbroken” or closed connection of electrical components that form a continuous conducting path for current to flow; if the circuit is “broken” (or open as in an open circuit) no current can flow and no power or energy can be delivered.
The most basic electrical circuit is made up of a power source (like a battery) attached to a load (like a resistor).
What is a Load?
A load is a device that absorbs the power coming from a power source and uses the power to do work, like spin a motor, or simply dissipate the power into heat like the coils of wire in a toaster. In all cases, loads are used to both consume and regulate the power being produced. Generally speaking, a load is measured as resistance in units called ohms.
In relative terms, a “light” load has a large resistance and a “heavy” load has a small resistance. This may be counter intuitive, but it is the case, nevertheless. For example, a 100 ohm resistor presents a “lighter” load to a circuit as compared with a 10 ohm resistor. The motor-propeller is about 2 to 4 ohms making it a very heavy load.
What is a Series Circuit?
In an electrical circuit several devices such as light bulbs can be placed in a line - or in series - between the positive and negative poles of the battery. This is called a series circuit.
A major problem is if one light bulb burns out, then it acts like a switch and turns off the whole circuit. On the other hand a major advantage of a series circuit is that it saves wires that are needed in a parallel circuit.
What is Power?
Power is the combination of voltage and current. Voltage is the pressure component of power forcing electrons to move through a circuit, and current is the quantity component of power indicating the amount of electrons in the flow. Both voltage and current are required to produce the electrical force called power. Power is instantaneous and is not measured over time like energy. When you measure power, you measure voltage and current for a given instant of time.
This is an important distinction – time, or lack of it, is the essential difference between power and energy. Power is instantaneous while energy is power measured over time.
Electrical power is measured in units called watts.
What is a Parallel Circuit?
Devices can be arranged in a parallel circuit such that if any bulbs burn out the circuit still remains intact and operates. Holiday lights are wired in parallel so that if one bulb burns out the others remain lit.
The circuit below shows two lights wired in parallel. If one light burns out the other one stays on.
What is Energy?
Energy is power over time. Energy is the power flowing through a circuit for a given time like one second, one minute or one hour. When we speak of energy we mean power times time.
Energy is measured in units similar to power but with a time component as in watt-seconds (or Joules), watt-minutes or watt-hours.
If a circuit generates 1 watt of power for 1 hour, it is said to generate 1 Watt-Hour of energy. If an electric meter measures power in Watt-Hours (3600 Joules), that can be converted to any other time frame by understanding how time is measured – one hour = 3600 seconds. Energy can be measured in Joules (watt-seconds).
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