Recently in my school, I tried to generate electricity from plants in a flower pot with copper and Zinc electrodes. The Potential difference in the voltmeter read 2 to 3 volts but when I connected the a small motor to it , it did not work. Though Potential difference was produced, there was no current. What could be the reason? How can I solve this problem and rotate the motor?
I don't agree with the above answer, sorry EUGenius. The reason is the battery cannot produce enough electrons (current) and the motor shorts it out, there is a small amount of current but not enough. And more water to the pot and use a bigger surface area of metal, add lemon juice but it might harm the plant. See lemon battery in google.
Power (P) = Voltage (V) x Current (I)
Since Voltage (V) = Current (I) x Resistance (R),
Power (P) = Voltage (V) ^ 2 / Resistance (R)
Since the power seems to be negligible, but there is a voltage present, this means:
0 = V^2 / R
0 = I^2 x R
Therefore your resistance must be extremely high for this to happen. Also, you do need a certain minimum power in order to start operating the motor. To increase your power, you could either increase the current (by adding more electrodes, increase the concentration of flower pots, etc.) or decrease the resistance in your circuit (by using more conductive wires).