Q: How long it takes to charge up a cellphone with a generator? (answer at the end.)

 

Introduction:

This lab we are going to generate power with a hand generator. Inside of a generator there is a magnet that moves back and forth inside a coil of wire. When we are shaking the generator the magnetic field will change as the magnet pass through the coil and the change of magnetic field will generate voltage. According to the Faraday’s Law that changing magnetic fluxes through coiled wires generate electricity also known as current and voltage. The greater it changes, the more power will generate. With NXT adapter we will be able to collect data to see how much power we have generated.

Equipment:

One generator

one voltage probe

one NXT adapter

NXT

labview VI

Excel sheet

Procedure:

1. We are provided a labview file, generator_lab.vi, to record our data. Before we start we need to understand how the file works. Once the program is running we will have 30 seconds to record the data. Each second the program will show the voltage that generated. Then VI will export the data to excel file.

2. After we connect the generator to NXT at the 1 terminal and connect the NXT to the computer we are now able to record the data. First we will shake the tube at a particular rate. As we shaking it we will also need to count the number of shake within 30 seconds.

3. After we run the program and record the data on VI there will be 30 data points each represent how much voltage you create in one second. Then We can export the data to excel, calculate the sum of the squares of the voltages (SSV). Repeat above steps 3 more times but each times with different rates of shakes.

4. After we find each SSV we are going make a plot to show our result with linear curve.

 

Data:

The above data table provide the proof of Faraday’s law. It shows that when the magnet inside the tube is moving forward (upward) the value we get it positive, but when the magnet is moving backward (downward) we will have negative result because the changing magnetic field can be negative. The coil in the tube did not change the direction of current flow therefore when the magnet is moving the opposite direction the data will have negative result. When we calculate the sum of squares of the voltages negative value will become positive. The table also shows us that with the number of shake increase are also increasing the generate energy.

# of shake		sum of the squares (v)
16		0.61
26		0.895
40		1.619
80		3.493
100		8.423

This table will have a better view about when the number of shakes increase the sum of the output voltage increases.

The graph shows us the generated voltage is directly proportional to the number of shakes. As the number of shakes increases the more voltage we will generate, therefore the graph gives us linear relationship.

 

We are using about 80 mA and 110 v as input to charge up a cell phone. We need about 3 hours to get it fully charged, therefore 0.08 A*110 v = 8.8 W. With 3 hours 8.8 w *3 = 26.4 watt-hour, and it is about the same that supplying 50 watt light bulb for 30 minutes. As we can see we were be able to generate 8.423 v with 100 shakes in 30 second. So at this rate we will be able to charge a phone in 8.432 v*0.08 A=0.67456 w, and 26.4/0.67456 = 39.16 hours. So with in 40 hours with 200 shakes per minutes and no rest we will be able to charge our phone.

A: 40 hours.

Conclusion:

This lab is helpful to me to have a better view about green energy and also have a better idea how much work needed to provide certain amount of energy. It is interesting to see how much energy we will be able to produce in short amount of time. After this lab we are also be able to know the precious of energy.