Evaluation in the experiment of exploring the relationship between current and resistance (1) the voltage at both ends of the constant resistance is changed by changing the number of batteries in series (2) the voltage at both ends of the constant resistance is changed by changing the size of the sliding rheostat Evaluate these two ideas

Evaluation in the experiment of exploring the relationship between current and resistance (1) the voltage at both ends of the constant resistance is changed by changing the number of batteries in series (2) the voltage at both ends of the constant resistance is changed by changing the size of the sliding rheostat Evaluate these two ideas

It is not suitable to change the voltage by changing the power supply
And series a sliding rheostat, because the voltage is proportional to the resistance, so this method to change the voltage is the best

If the resistance in the circuit becomes small and the current becomes large, how does the voltage change

It's getting lower

In a circuit, the resistance increases, the current increases, so how does the voltage change?
Can we get it according to Ohm's law? Doesn't it mean that there must be a fixed quantity? If all three quantities change, how can we judge that

It's hard to say. In fact, I've been bothered by the question you asked. A circuit already means that some things are fixed, and the specific is more customized. You will find that this question is meaningless. For example, in a question, the total electric compaction is unchanged, and you can push others by changing a condition

Two resistance wires, the ratio of which is 2:1, are connected in parallel to the circuit with voltage of U
Then at the same time, the ratio of heat they emit is 1:2. Why?

Two resistance wires, the ratio of which is 2:1, are connected in parallel to the circuit with voltage of U
In the same time, the ratio of heat released by them is 1:2
W=t*U^2/R
W1=t*U^2/R1
W2=t*U^2/R2
W1/W2=(t*U^2/R1)/(t*U^2/R2)=R2/R1=1/2