500
Mr. Han thinks that the "Quantum" Duracell battery has more energy than the regular Duracell battery. He wants to test out his hypothesis by doing the following experiment.
He will use one new "Quantum" battery to power a flashlight and a old regular battery to power a clock. He leaves the flashlight and clock on until it turns itself off. He will record the time.
How can you make this experiment into a control experiment?
Both batteries are new. Both batteries being used with the same device.
Only thing that changes is the type of battery.