Actually, two of the statements can be argued to be true:
1)Changing several different factors in an experiment takes too many controls.
This means that for every factor that is changed you need a control which has all the other factors stable - but with many factors, this might be undoable.
2) - and this is the best answer:
When only one factor is changed, you can be more certain that it caused the results.
If this factor is the only thing that changes, you can safely assume that it caused the results!
The power dissipated by the motor is given by:
where V is the voltage of the battery and I is the current flowing in the circuit.
In our problem, the voltage is V=12 V and the current is I=246 A, so we can calculate the power dissipated by the motor using the previous equation:
A perfect black body can’t be realized
Thomson. J. J. Thomson took science to new heights with his 1897 discovery of the electron – the first subatomic particle. He also found the first evidence that stable elements can exist as isotopes and invented one of the most powerful tools in analytical chemistry – the mass spectrometer.