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Electrolyte Challenge: Orange Juice Vs. Sports Drink

Difficulty
Time Required Short (2-5 days)
Prerequisites None
Material Availability You will need a digital multimeter for this science fair project. See the Materials and Equipment list for more details.
Cost Average ($40 - $80)

Abstract

The makers of sports drinks spend tens to hundreds of millions of dollars advertising their products each year. Among the benefits often featured in these ads are the beverages' high level of electrolytes, which your body loses as you sweat. In this science project, you will compare the amount of electrolytes in a sports drink with those in orange juice to find out which has more electrolytes to replenish the ones you lose as you work out or play sports. When you are finished, you might even want to make your own sports drink!

Objective

To investigate whether or not a sports drink provides more electrolytes than orange juice.

Credits

David Whyte, PhD, Science Buddies

This project is based on the following 2008 California State Science fair project, a winner of the Science Buddies Clever Scientist Award:
Yaeger, T.O. Jr. (2008). Electrolyte Madness.

Cite This Page

MLA Style

Science Buddies Staff. "Electrolyte Challenge: Orange Juice Vs. Sports Drink" Science Buddies. Science Buddies, 18 Nov. 2014. Web. 26 Nov. 2014 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/Chem_p053.shtml?from=AAE>

APA Style

Science Buddies Staff. (2014, November 18). Electrolyte Challenge: Orange Juice Vs. Sports Drink. Retrieved November 26, 2014 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/Chem_p053.shtml?from=AAE

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Last edit date: 2014-11-18

Introduction

"Just do it!" You have probably heard that slogan, and there is no doubt that exercise is a key part of staying healthy. But exercising depletes the body's stores of fluids and minerals, which must be replaced. Most experts agree that if you are engaged in light to moderate exercise, drinking a glass or two of water should do the trick. But if you are exercising strenuously, you also need to replenish some of the salts that your body loses through sweat. These salts, or electrolytes, are found in most sports drinks.

What advantages does a sports drink have over water? Water provides the liquid you need to avoid dehydration, but it does not have electrolytes. An electrolyte is a substance that will dissociate into ions in a solution. The ions in the solution give it the capacity to conduct electricity. Electrolytes, such as sodium and potassium, are present in sweat. Chloride, calcium, and phosphate ions are also electrolytes.

The proper concentration of electrolytes in your blood is essential to your health. Your cardiovascular and nervous systems, to name just two, require electrolytes to function well. Differences in the concentration of sodium and potassium inside and outside of cells allow your nerve and muscle fibers to send electrical impulses (which is how these cells communicate and get your body to react and move).

Your body keeps the concentration of the various electrolytes in its fluids within a narrow range, and this process depends on consuming enough water and electrolytes. The maintenance of electrolytes within this narrow range is due to the body's homeostatic mechanisms, which control the absorption, distribution, and excretion of water and its dissolved electrolytes.

But can you get your electrolytes from natural juices, such as orange juice? Yes and no. One problem with juices is that many have relatively high concentrations of carbohydrates, which is fine for your morning drink, but not ideal for rehydrating during exercise. High levels of carbohydrates add useless calories and require water for digestion.

To measure the electrolytes in this science project, you will use a multimeter. A multimeter is an electronic device that measures voltage, current, and resistance. For this project, you will use just the ammeter part of the multimeter. An ammeter measures current.

How can you use an ammeter to measure the concentration of electrolytes? You will use it to measure conductance, which is proportional to the electrolyte concentration. Because electrolytes are charged particles that carry current in solution, the conductance of the solution depends on the concentration of the electrolytes. If you increase the concentration of electrolytes in a solution, the conductance of the solution also increases. In order to measure a current in the solutions, you have to apply a voltage. You will use a 9-volt (V) battery to supply the voltage.

Conductance is measured in units, called siemens, and has the symbol G. The symbol for current is I, and it is measured in amperes (amp). Voltage, V, is measured in volts. Calculating the conductance is easy—it is the current divided by the voltage, as shown below in Equation 1 below.

Equation 1.

Conductance (siemens) =   Current (amps)
Voltage (V)


G =    I 
V
  • G is conductance, measured in siemens.
  • I is current, measured in amperes.
  • V is the voltage, measured in volts.

Terms and Concepts

  • Electrolyte
  • Dissociate
  • Ion
  • Solution
  • Conduct electricity
  • Electricity
  • Homeostatic mechanism
  • Multimeter
  • Voltage
  • Volts (V)
  • Current
  • Amps, microamps, milliamps
  • Resistance
  • Ohms
  • Ammeter
  • Conductance
  • Proportional
  • Siemens
  • Direct current
  • Alternating current
  • Open circuit
  • Electrolysis
  • Dilute

Questions

  • What are the amounts of sodium, potassium, and carbohydrates in one serving (8 ounces [oz.]) of orange juice? How does this compare with sports drinks?
  • What do electrolytes do in your body?

Bibliography

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Materials and Equipment Product Kit Available

These specialty items can be purchased from the Science Buddies Store:

  • Electrolyte Challenge kit (1). Includes:
    • Digital multimeter
    • Alligator clip leads (2; colors may vary)
    • Copper wire, bare, 24-gauge (1.5 meters [5 feet])
    • 9 V battery
    • 9 V battery clip

You will also need to gather these items:

  • Disposable plastic straw
  • Scissors
  • Small plastic, glass, or ceramic bowls, not metal (8)
    • Use a different one for each liquid you test or use one bowl repeatedly being careful to wash and wipe it thoroughly between liquids.
  • Masking tape or other materials for creating labels
  • Permanent pen or marker
  • Distilled water (dH2O), room temperature; available in the bottled water section of most grocery stores
  • Tap water, room temperature
  • Sports drink(s) of your choice, room temperature
  • Orange juice of your choice, room temperature
  • Paper towels
  • Lab notebook

Order Product Supplies

Buy Kit
Project Kit: $29.95

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Experimental Procedure

Making a Simple Conductance Sensor

  1. Using the scissors, cut a 5 cm (2 inch) piece from the drinking straw.
  2. With the scissors, cut two pieces of copper wire, each about 12 cm (6 inches) long.
  3. Make a conductance sensor like the one shown in Figure 1 below:
    1. Wrap one piece of wire around the 5 cm straw piece near one end a few times, leaving a 5 cm (2 inch) tail of wire.
      1. Wrap the wire snuggly around the straw. If the wires on the conductance sensor move while you are taking measurements, your measurements may be inaccurate.
    2. Wrap the second piece of wire around the other end of the straw tube a few times, leaving a 5 cm (2 inch) tail of wire. There should be no contact between the wires, and they should be wrapped tightly enough that they will not slide off the tube.
      1. Caution: Make sure the two wires do not touch. The conductance sensor will not work if the wires touch, and touching wires will blow the fuse in your multimeter.
Figure 1: conductance sensor for measuring ions in solution
Figure 1. The conductance sensor consists of a non-conducting core, a piece of disposable drinking straw, with copper wire wrapped around the ends. The ions in the solution complete the circuit, enabling current to flow between the copper wires.

Making a Conductance Measuring Circuit

  1. Start assembling the conductance measuring circuit by attaching the battery clip to the 9 V battery.
    1. A schematic diagram of the main components of the circuit can be seen in Figure 2 below. Figure 3 below also provides a detailed picture of the entire circuit. Refer to Figures 2 and 3 as you assemble your circuit.
Electrolyte challenge science fair project circuit schematic
Figure 2. This diagram schematically shows how the conductance measuring circuit should be built. Use alligator clips to connect the multimeter, battery, and conductance sensor. Make sure to connect the positive (+) terminal of the battery with the positive (+) terminal of the multimeter.

Figure 3: science project setup for measuring ions in solution
Figure 3. This photo shows an example of the completed conductance measuring circuit. (Note: the color of the alligator clips does not matter and does not need to match the color of the multimeter probes or the battery leads.)
  1. Plug the multimeter test leads into the multimeter.
    1. Science Buddies Kit: For the multimeter in the kit, the black (negative) multimeter probe goes in the hole labeled "COM" at the bottom left of the multimeter. The red (positive) multimeter probe goes in the middle of the three holes (the hole labeled VΩmA). See Figure 3 above.
    2. If you are not using the Science Buddies Kit, consult the manual that came with your multimeter to see which jack should have the positive versus negative probe.
    3. Tip: Make sure the multimeter probes are plugged into the correct jacks, or your experiment will not work. For additional information about using a multimeter consult the Multimeter Tutorial.
  2. Use one of the pairs of alligator clips (any color) to connect the positive (red) wire of the 9 V battery clip to the positive (red) multimeter probe. To do this, clip one of the alligator clips to the positive (red) wire of the 9 V battery clip, and clip the other end of the pair of alligator clips to the metal part of the positive (red) multimeter probe.
    1. In Figure 3 above, the red pair of alligator clips makes these connections. Neither the color nor the actual use of alligator clips is crucial, as long as you make the same connections.
    2. Make sure to clip the alligator clips to the metal part of both the multimeter probe and 9 V battery clip. The circuit will not work if the alligator clips are not connected to the metal parts of the probe and clips leads because the circuit will not be complete.
  3. Using the second pair of alligator clips (any color), attach one of the copper wire tails of the conductance sensor to the negative (black) probe of the multimeter. You can use either tail of the sensor. To do this, clip one of the alligator clips to one of the wire tails of the conductance sensor, and clip the other end of the alligator clips to the metal part of the negative (black) multimeter probe.
    1. In Figure 3 above, the black pair of alligator clips makes these connections. You do not have to use a black pair of alligator clips, but you should make the same connections.
Figure 4: connect conductance sensor and battery
Figure 4. Twist one copper wire end of the conductance sensor around the metal part of the battery cap's black lead.
  1. Twist the other wire tail of the conductance sensor around the metal end of the black lead from the 9 V battery clip as shown in Figure 4 below.
  2. Double-check your connections to make sure they match those in Figure 3 above. The colors of the alligator clips are not important, but the order of the connections is: the red probe of the multimeter should be connected to the red lead from the battery clip, the black lead of the battery clip should connect to one of the wire tails of the conductance sensor, and the other wire tail of the conductance sensor should connect to the black multimeter probe.
    1. Note that this is an open circuit because of the gap between the wires wrapped around the non-conducting tube. You will use the electrolytes in the solutions to close the circuit. The amount of current that flows is proportional to the electrolyte concentration.
  3. Important: never let exposed metal from the red or black multimeter probes/alligator clips, or the conductance sensor wires, touch each other directly. This will create a short circuit. Since the circuit contains a 9V battery, this could damage your multimeter by blowing out the fuse. Always keep the red and black wires a safe distance away from each other, as shown in Figure 3.

Setting Up Your Test Solutions

  1. Clean the eight small bowls with warm soapy water, rinse thoroughly, and dry them right away with a clean dry cloth or paper towel. This will remove ions in the tap water. If you want to be extra careful, rinse the bowls with distilled water before drying.
  2. Put masking tape on all eight bowls.
    1. Label four bowls with the following labels: Distilled Water, Tap Water, Sports Drink, and Orange Juice.
    2. Label one bowl Tap Water Rinse.
    3. Label the final three bowls as follows: dH2O Rinse 1, dH2O Rinse 2, and dH2O Rinse 3. Use these bowls to rinse the conductance sensor between uses.
  3. Pour each liquid into the appropriately labeled bowl. All of the solutions should be at room temperature. Each bowl should contain enough liquid to completely submerge the straw part of the conductance sensor as shown in Figure 3 above.

Measuring the Conductance

  1. Turn the multimeter to read DCA (direct current). Make sure it is reading direct current (DCA) and not alternating current (see the instructions for your multimeter).
    1. For measuring distilled water, the meter should be set to DCA 200 microamps (200µ). For measuring the tap water, orange juice, and sports drink samples, the meter should be set to a higher setting, like DCA 200 milliamps (200m).
      1. For an indepth explanation of how to use a multimeter see the Multimeter Tutorial.
      2. The FAQ for this Project Idea also has more details and troubleshooting advice about using the multimeter for this particular project.
  2. Place the conductance sensor in the distilled water. Make sure the sensor tube is completely immersed.
  1. Read the current on the multimeter. If you are not using an auto- ranging multimeter, move the dial to its highest sensitivity (e.g., 200µ).
    1. Always make your readings quickly and remove the conductance sensor from the solutions immediately. Over time, the copper wires will start to dissolve in the solutions, skewing your results. In addition, electrolysis may take place, forming tiny bubbles on your conductance sensor that can interfere with your data.
  2. Record the current (the readings from your multimeter) in your lab notebook in a data table. Make sure to record the units you are using (either microamps or milliamps) so that you can plug it in to the equation correctly later.
  3. No need to rinse this time because you used distilled water.
  4. Now place the conductance sensor in the tap water.
  5. Record the current. Again, make sure you are using the proper sensitivity scale. You will need to use a lower sensitivity for tap water (e.g., 200m) than you used for distilled water.
  6. Tap the sensor on a paper towel to remove drops of tap water. Then rinse the sensor in distilled water, dipping it briefly in each of the three distilled water rinse bowls.
  7. Place the sensor in the sports drink and measure the current. Record the current in your lab notebook.
  8. Tap the sensor dry, and then dip the sensor in tap water, then in the three bowls of distilled water.
  9. Place the sensor in the orange juice and measure the current. Record the current in your lab notebook.
  10. Rinse the sensor in the tap water and then in all three distilled water bowls.
  11. Repeat steps 1-12 in the "Measuring the Conductance" section two more times to obtain a total of three measurements for each liquid. Record all data and measurements in the data table in your lab notebook.
  12. Average your results across the three measurements for each liquid.
  13. Convert microamps to amps by dividing by 1,000,000. Convert milliamps to amps by dividing by 1,000.
  14. Calculate the conductance for each liquid by using Equation 1, shown in the Introduction.
    1. The current (I) for each liquid is the average amps that you calculated.
    2. Since the voltage was always from your 9 V battery, you can use 9 V as the voltage (V) in your calculations. In reality, the voltage is likely to be slightly less than 9 V due to internal resistance of the battery. But this change is quite small and nearly constant across the experiment. Because it is so small, you do not need to take it into account. If you have a second multimeter though you can adapt the circuit to monitor both current and voltage across the battery.
  15. Which liquid has the highest conductance, meaning the most electrolytes?

Troubleshooting

For troubleshooting tips, please read our FAQ: Electrolyte Challenge: Orange Juice Vs. Sports Drink.

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Variations

  • Try other sports drinks and juices.
    1. What is the conductance of fresh-squeezed orange juice?
    2. What about the conductance of lemonade?
  • Try making your own sports drink, starting with orange juice. If the carbohydrates in the orange juice are higher than they are in the sports drink, dilute the juice with distilled water so that the carbohydrates are about the same as they are in the sports drink. How does the conductance of the diluted juice compare to that of the sports drink?
  • Make a conductance sensor using a microphone jack.
  • Standardize your readings, using tap water as a reference. Divide all of the current measurements for each trial by the current you measured for the tap water. Tap water will have a conductance of 1.0. The fruit juice and sports drinks will then have conductances that are multiples of the tap water's conductance.

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Frequently Asked Questions (FAQ)

If you are having trouble with this project, please read the FAQ below. You may find the answer to your question.
Q: How many alligator clips do I need? Do I need insulated clips (i.e., clips with a rubber coating)?
A: If your digital multimeter does not have alligator clips on it, you will probably need at least two alligator clips, as shown in Figure 3 in the Experimental Procedure. If your multimeter already has alligator clips, then you should only need one alligator clip (to connect the conductance sensor to the positive terminal on the 9 V battery). Because this experiment deals with very low voltage and current levels, insulated clips are not necessary, but be sure not to let the connections touch!
Q: Why is it important to keep the wires on the conductance sensor from moving?
A: If the wires on the conductance sensor move while you are taking measurements, your measurements may be inaccurate. Make sure the wires are tightly secured on the ends of the conductance sensor by attaching the short end of the wire to the longer end by twisting the two together or by using a very small drop of super glue to hold the wires in place.
Q: What is the purpose of dipping the sensor in distilled water? Should I replace the distilled water between tests?
A: Dipping the sensor in distilled water removes all of the ions and other liquids from the sensor. Not rinsing the sensor will cause the sensor to become contaminated with different liquids between the different tests, which could make your results have higher or lower conductance values than they actually do. Although it is not necessary, changing the distilled water in the rinsing bowls between tests may improve accuracy.
Q: What does it mean if I am getting a negative current reading on my multimeter?
A: The wires in the circuit may be connected incorrectly. Make sure that the positive node of the battery is attached to the red wire (+) from the multimeter. If you have a negative connected to a positive (for example, a black wire [-] connected to the positive node on the battery), it will give you a negative current reading.
Q: I'm not sure if my multimeter is set up correctly. How should it be configured?
A: If this is your first time using a multimeter, we recommend that you read the Science Buddies Multimeter Tutorial. For this project, the black multimeter probe should be inserted into the hole on the bottom of the multimeter labeled "COM" and the red multimeter probe should be inserted into the hole next to it it labeled "'VΩMA". To measure the current of your samples, make sure the multimeter dial is set to the direct current (DC) amperage area, represented by an A with solid and dashed lines next to it. Set it to the 200 milliamps setting (labeled 200m) to measure your samples (except for measuring the distilled water, when it should be set to the 200 microamps setting, labeled 200μ). The multimeter from the Science Buddies kit is shown in Figure 5, below. Notice that the DC amps settings are labeled in green text on the right-hand side of the dial.

Chem_p053 FAQ image
Figure 5. Proper setup for the multimeter included in the Science Buddies kit. Other multimeters may be similar. The black multimeter probe goes in the hole labeled "COM" on the bottom left of the multimeter. The red multimeter probe goes in the middle of the three holes labeled VΩMA. For measuring your tap water, orange juice, and sports drink samples the meter should be set to 200m, which means the meter is measuring current in the 200 milliamp range. For measuring distilled water, the meter should be set to 200μ, which means the meter is measuring current the 200 microamp range.
Q: I'm not getting any readings from my multimeter. What should I do?
A: If you turn on your multimeter to the 200m setting as shown above, you should see it read "00.0" on the display. If you see no reading at all this suggests that there is a problem with the multimeter. One possible problem is that the battery that powers the multimeter is not making a good connection with the battery contacts. Sometimes battery contacts get a thin layer of oxide that creates enough resistance to prevent current flow. Try the following steps:
  1. Unscrew the battery housing and remove the battery.
  2. Clean the battery contacts and the terminals of the battery by rubbing them with a pencil eraser. This should remove any oxide.
  3. Replace the battery and screw the battery housing closed again.
  4. Try turning on the multimeter again. If the multimeter display now reads "0" the problem has been solved.
If, after cleaning the battery and battery contacts, the multimeter display still does not read "0" it is likely the multimeter is defective. If you have tried the steps above and feel that you have a defective multimeter in a Science Buddies kit please contact help@sciencebuddies.org.
Q: Why am I getting a reading of 0 from the multimeter no matter which solution I measure conductance for?
A: A number of different issues may result in a reading of 0 from the multimeter regardless of the solution's real conductance:
  • One or more of your connections may not be attached securely. Double-check all the connections.
  • Your multimeter may not be set to a sensitive enough setting. The currents flowing through the liquids in this experiment are very small, so your multimeter must be set at a high sensitivity, such as 200 milliamps (mA) (or 200 microamps [μA] for distilled water).
  • Your 9 V battery might be dead. You can check whether your battery still works by setting your multimeter to a scale that can read 10 volts (possibly a 20 V scale) and placing the positive (red) multimeter terminal on the positive battery node, and the negative (black) multimeter terminal on the negative battery node. If the reading is below 6, your battery may not have enough power for this project and you should use a fresh battery.
  • Your multimeter may have blown a fuse. The fuse contains a thin wire that burns out if too much current flows through it, in order to protect the rest of the multimeter's circuitry. When the experiment is set up as described but the two sensor wires touch (the ones in the liquid), it will blow the fuse, so be careful that they do not touch. If your multimeter was working well and then suddenly starting reading 0 all the time, then you probably blew the fuse in your multimeter. See the question "How can I tell if I blew the fuse in my multimer?" below to confirm if you blew the fuse. The fuse in the multimeter from the Science Buddies kit cannot be easily replaced because it is soldered directly to the circuit board. If you purchased the Science Buddies kit and think you blew the fuse in your meter, please contact help@sciencebuddies.org for assistance.
  • The wires on your conductance sensor may have become compromised in some way. There should be no material collected on them; if there is anything collected on them, clean and rinse them well and try again.
  • Make sure that the wire you have wrapped around the ends of the conductance sensor is "bare" and has no insulation on it.
Q: Why are my multimeter readings going up and down?
A: A few possibilities could explain why your readings are fluctuating; you can determine what is happening in your experiment by how much the readings are changing.
  • It is normal to have very small fluctuations (i.e., the reading stays around the same number but increases or decreases slightly). In these types of experiments with multimeters, it can be very difficult to get an entirely stable current.
  • If your measurements decreased quickly, you may have encountered a problem with electrolysis. Electrolysis is when water is broken up into hydrogen and oxygen gas by an electrical current. If electrolysis is occurring, there will be little bubbles collecting on the wires on the ends of the conductance sensor. Electrolysis will result in a smaller surface area on the wires on the conductance sensor, and your readings will decrease.
  • If the wires on the conductance sensor move while you are taking measurements, this can make your measurements randomly vary from sample to sample. To fix this, see the answer for the question above on "Why is it important to keep the wires on the conductance sensor from moving?"
Q: The current readings on my multimeter seem very low for all of my samples and there is not much variation between them. What should I do?
A: Your multimeter may not be configured correctly. To check this, see the answer for the question above on "I'm not sure if my multimeter is set up correctly. How should it be configured?" Alternatively, the 9 V battery you are using may be dead. To test the battery, see the third answer for the question above on "Why am I getting a reading of 0 from the multimeter?"
Q: I'm not sure if the values I am getting are correct. How should I be making my calculations and what is the range that my results will probably fall in?
A: If you take your measurements using the 200 milliamps setting, your current readings will be in milliamps. (If you used the 200 microamps setting with the distilled water, your current readings will be in microamps.) For this experiment, current readings in the range of 0 (for distilled water) to 100 milliamps are expected.

To calculate the conductance of your different samples, use Equation 1 from the Introduction: Convert your current readings (in milliamps or microamps) to amps and divide this by the voltage of your battery (which should be about 9 V, but you can measure this with your multimeter to be sure). This will give you conductance in siemens (which you can convert to millisiemens by multiplying by 1,000). For this experiment, conductance results up to around 2.0 millisiemens are expected.
Q: I can't find 24 gauge copper wire. Can I substitute a different gauge?
A: Yes, you can make substitutions — the exact resistance of the wire is not critical in this experiment, so the gauge of the wire does not matter. 24 gauge wire is easy to work with, which is why we recommend it. But 22 (slightly thicker) or 26 (slightly thinner) would also be fine. If your wire gets too thick (i.e. 18 gauge), it will be difficult to wrap around the straw and the battery pack lead, as seen in Figures 1 and 4 of the procedure. If it gets too thin (i.e. 30 gauge), it can be fragile and easier to break. Just make sure that you use bare copper wire with no insulation. "Hookup wire" (with plastic or rubber insulation) and "magnet wire" (with enamel insulation) will not work for this project.
Q: I can't find solid-core wire. Can I use stranded wire instead?
A: Solid wire means that the core of the wire is made up of a single, solid piece of metal. However, you can also find stranded wire, where the wire is actually made up of many smaller wires twisted together, like a rope. Either type of wire will work for this project as long as it is not insulated.
Q: How can I tell if I blew the fuse in my multimeter?
A: Follow these steps:
  1. Set your multimeter to measure DC current in the 200 mA range (the dial setting labeled "200m" on the right, if you are using the Science Buddies kit).
  2. Plug the multimeter's black probe into the port labeled COM.
  3. Plug the multimeter's red probe into the port labeled VΩMA.
  4. Tightly wrap one lead from the resistor around the end of the black probe tip, as shown in Figure 7 below.
  5. Attach the snap connector to the 9 V battery.
  6. Use a black alligator clip lead to connect the free lead from the resistor to the black lead from the 9 V snap connector.
  7. Use a red alligator clip lead to connect the multimeter's red probe to the snap connector's red lead.
  8. Your multimeter should read about 9 mA (maybe slightly less if you are not using a fresh battery).
    1. If this works, then you know there is nothing wrong with your multimeter. If you are having trouble with your experiment, the problem is with something other than the multimeter.
    2. If this does not work, and you are confident that you set up the test correctly as shown in Figure 6 below, please contact help@sciencebuddies.org for assistance.
  9. When you are done, disconnect the alligator clips so you do not drain the 9 V battery, and remember to turn your multimeter off.
setup to determine if a multimeter has a blown fuse
Figure 6. Setup for making sure the multimeter has a working fuse.

1k resistor wrapped around multimeter probe
Figure 7. A close-up picture showing one of the resistor's leads wrapped around the black multimeter probe tip.

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