Final answer:
The correct hypothesis is that if resistance increases, electron speed decreases, as higher resistance opposes electron flow, reducing current according to Ohm's law.
Step-by-step explanation:
The hypothesis that is supported by the observations of the teacher demonstrations is: If the resistance in a circuit increases, then the speed of the electrons decreases. This is because when resistance increases, it opposes the flow of electrons, causing them to move more slowly through the circuit. According to Ohm's law, the current in a circuit is directly proportional to voltage and inversely proportional to resistance. Therefore, if the resistance increases while the voltage remains constant, the current, which is the flow rate of electrons, must decrease. This relationship can be demonstrated by the equations I = V/R, where I is the current, V is the voltage, and R is the resistance. To further clarify, in a parallel circuit, if you remove a resistor, the total resistance decreases, but if resistors are in parallel and you increase the resistance of one resistor, the current through the other resistor will decrease while voltage remains the same, once again showing that higher resistance affects the current flow negatively.