Name:______

Period:______

Fuel Cell Car Lab: Making a fuel cell crane and measuring power

Objectives:

1. Students will convert the fuel cell car into a crane

2. Students will measure the power of the fuel cell crane

Background:

In the previous exercises we learned about how fuel cells can be used to convert hydrogen to electricity to power a motor-driven device such as a car. In this lab we will turn the fuel cell car into a crane. We can also calculate the power of the crane by simply measuring how fast the crane can lift an object of a given mass over a measured distance.

You will need the following materials:

• Solar panel

• Electric Light (60-100 watt bulb)

• Car body with fuel cell

• Syringe with tubing nozzle

• Distilled water (Use only distilled water for experiments with the fuel cell. The water must be free of all ions and salts or it can destroy the fuel cell. NEVER USE WATER FROM THE TAP OR BOTTLED DRINKING WATER.)

• A long piece of string

• Tape

• Several weights to lift with the crane (Large binder clips work well)

• Meter stick

• Stop watch

• Balance

Setting up:

1. Set up the fuel cell car and fill up the tanks completely with hydrogen and oxygen as we learned in the previous exercise. Do not connect the motor wires until you have set up your test course (see the following steps).

2. Position the car so that the front wheels barely hang over the edge of the table. Someone from the group should HOLD the car at all times so that it does not fall off the table. When the motor is running, the wheels should not rub against the edge of the table.

3. Use a small piece of tape to connect the string to the red spool on the front axel.

4. Test the crane by plugging in the wires for the motor -- again: red wire to the red side of the call, black wire to the bluish gray side, as shown at right. The wheels should begin to move wh en the second wire is attached. Keep some tension on the string by tugging gently to keep it winding properly.

5. To stop the crane, simply unplug the motor.

6. To unwind the crane, simply plug the motor in the opposite way: red wire t o black side, black wire to red side. Do not pull the rope out without operating the motor as it can damage the motor.

Measuring the power of the crane:

Power is defined as the amount of energy transferred per unit time. The more powerful the motor, the faster a given weight will be lifted.

P= E / t (Equation 1)

When an object is raised from the ground to a height off the ground, it experiences a change in potential energy. Recall that potential energy is the amount of energy an object has due to its position. Potential energy (Epot) can be calculated by multiplying the mass (m) of the object that is moved by the acceleration due to gravity (g) and by the height (h) in meters that the object is moved.

Epot = m * g * h (Equation 2)

1. Obtain two or three large binder clips and clip them to the end of the string. Wind the string so that it is taught.

2. You will now lift the object a carefully measured distance while recording the speed at which the object travels that distance.

3. One member of the group should be responsible for holding the car and plugging and unplugging the wires to start and stop the crane. Another member should be responsible for measuring the distance the object is lifted.

4. When everyone is set, start the stopwatch at the same time the crane is plugged in and stop the watch when the object reaches the designated height.

Data:

Total mass of objects (in kg): ______

Height object traveled (in m): ______

Time object traveled (in s): ______

Use equation 2 to calculate the Epot (note that the units will be kg*m2/s2 which is equivalent to Joules (J): ______

Now use equation 1 to calculate the power of the crane (note that the units will be in Joules/second (J/s) which is equivalent to watts (w): ______

Questions:

1. Does the power of the crane change when a heavier load is lifted? What happens to the power calculations if you repeat the experiment using additional binder clips?

2. What is the maximum load the crane is capable of lifting? Remember that the crane may not perform as well when it begins to run low on hydrogen fuel so make sure the tank is full.