Answer:
1) see the diagram below
2) (b) the length of the wire being tested
Step-by-step explanation:
1) An ammeter is connected in series with the circuit branch in which you want to measure current. "Conventional current" enters the positive terminal of the ammeter. (You can think of it as a voltmeter across a small resistor. The polarity of the voltage matches the polarity of the current.)
A voltmeter is connected in parallel with the circuit element of interest. Here, you want to measure the voltage across the wire, so the voltmeter is placed in parallel with the wire. The positive terminal of the voltmeter is connected to the end of the circuit element that has the higher (more positive) potential.
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2) The wording of the problem tells you which variable is independent:
"A varies with B" means the independent variable is B
Here, the independent variable is the length of the wire.