A researcher conducted an investigation to determine how varying the strength of an extern… — ACT

A researcher conducted an investigation to determine how varying the strength of an external magnetic field influences the thermal conductivity of a magnetite-based ferrofluid. In each trial, a ferrofluid sample of fixed volume ( $50\text{ mL}$ ) and fixed magnetite concentration ( $5.0\%\text{ v/v}$ ) was placed inside a thermal cell maintained at $25^\circ\text{C}$ . The applied magnetic field strength was varied from $0\text{ mT}$ to $200\text{ mT}$ in increments of $50\text{ mT}$ , and the resulting thermal conductivity of the ferrofluid was measured.

Match each experimental component on the left with its correct variable classification on the right.

Strength of the external magnetic field (in $\text{mT}$ )Independent Variable
Thermal conductivity of the ferrofluid (in $\text{W}/(\text{m}\cdot\text{K})$ )Dependent Variable
Ferrofluid sample volume and magnetite concentrationControlled Variable

Answer

Magnetic field strength matches Independent Variable; Thermal conductivity matches Dependent Variable; Sample volume and magnetite concentration match Controlled Variable.

In experimental design, the independent variable is the factor manipulated by the researcher (here, the external magnetic field strength). The dependent variable is the responding measurement (here, the thermal conductivity). Controlled variables are baseline conditions held constant across trials (here, sample volume, concentration, and temperature) to ensure valid comparisons.

Step-by-Step Solution

Identify the variable directly manipulated by the experimenter.

The researcher explicitly alters the magnetic field strength from

0\text{ mT}

200\text{ mT}

The variable intentionally varied across trials is the independent variable.

Identify the factor measured to evaluate the effect of the manipulation.

The resulting thermal conductivity of the ferrofluid is measured in response to field changes.

The observed outcome that changes in response to the independent variable is the dependent variable.

Identify parameters held constant across all experimental conditions.

Sample volume (

50\text{ mL}

), magnetite concentration (

5.0\%\text{ v/v}

), and cell temperature (

25^\circ\text{C}

) are kept identical in every trial.

Factors kept constant to ensure a fair test are controlled variables.

Key Concept

Experimental Variables (Independent, Dependent, and Controlled)

Estimated Time:1m 15s

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