Question

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a student lab group is brainstorming the design of an
experiment that uses an ammeter (measures current) and
different resistors to determine the effect of the resistance of
a resistor upon the current in a simple circuit. which post-it
note describes the most effective design?
choice 2 of 4:

• obtain a variety of batteries and build

several circuits. make sure that each
circuit has at least one resistor and make
sure that the resistance values are
different in the different circuits.

• place different ammeters in each circuit.
• measure the number of batteries and the

current for each of the circuits. record the
resistance values used in each of these
circuits.
check answer

Explanation:

To determine the most effective experimental design for investigating the effect of resistance on current, we analyze the key principles of a controlled experiment (keeping all variables constant except the independent variable, which is resistance here, and the dependent variable, which is current).

Step 1: Identify the Goal and Variables

The goal is to study how resistance (independent variable) affects current (dependent variable) in a circuit. For a valid experiment, all other variables (like voltage, ammeter, etc.) must be controlled (kept constant).

Step 2: Analyze the Given Design

The proposed design:

• Uses different batteries (which changes voltage, a critical variable).
• Uses different ammeters (which introduces variability in measurement tools).
• Measures batteries (voltage) and current, but changing batteries and ammeters means multiple variables (voltage, ammeter accuracy) are uncontrolled.

Step 3: Evaluate Against Experimental Design Principles

A valid experiment to test “resistance vs. current” requires:

• Constant voltage (same battery or fixed voltage source).
• Same ammeter (to ensure consistent measurement).
• Different resistors (to vary the independent variable).

The given design fails because it changes batteries (voltage) and ammeters, introducing confounding variables. Thus, this Post - it note does not describe an effective design (though the question implies we analyze this option; if this were a multiple - choice with other options, the correct one would control voltage and use the same ammeter while varying resistance).

(Note: Since the question asks to analyze this specific Post - it, the key takeaway is that this design is ineffective due to uncontrolled variables like voltage (from different batteries) and measurement tool (different ammeters).)

If we assume this is a multiple - choice where this is an incorrect option, the effective design would:

• Use the same battery (constant voltage).
• Use the same ammeter (consistent measurement).
• Test different resistors (vary resistance) and measure current.

But for the given option, the analysis shows it is flawed.

If forced to answer based on the provided option (even though it’s ineffective), but likely the question expects recognizing the flaws. However, since the user’s question is about this specific Post - it, the conclusion is this design is not effective because it fails to control voltage (different batteries) and measurement tool (different ammeters).

If we were to answer in the context of a multiple - choice where this is option B (for example), and the correct option would control variables, but based on the given info, the analysis of this option is as above.

(If the question is to judge if this is effective: No, because it does not control voltage (different batteries) and uses different ammeters, introducing extraneous variables.)

Answer:

This Post - it note does not describe an effective design. A valid design would control voltage (use the same battery), use the same ammeter, and vary only the resistor’s resistance while measuring current.