A group of materials engineers evaluated the power conversion efficiency of perovskite sol… — ACT

A group of materials engineers evaluated the power conversion efficiency of perovskite solar cells fabricated with different layer thicknesses of a titanium dioxide ( $\text{TiO}_2$ ) electron-transport layer ( $50\text{ nm}$ , $100\text{ nm}$ , $150\text{ nm}$ , and $200\text{ nm}$ ). All solar cell samples were constructed using identical perovskite absorber layers, tested under a constant simulated solar light intensity of $1,000\text{ W/m}^2$ , and maintained at a temperature of $25^\circ\text{C}$ . Which of the following correctly identifies the independent variable and the dependent variable in this experiment?

Independent variable: $\text{TiO}_2$ layer thickness; Dependent variable: Power conversion efficiencyAnswer
B
Independent variable: Power conversion efficiency; Dependent variable: $\text{TiO}_2$ layer thickness
C
Independent variable: Simulated solar light intensity; Dependent variable: Power conversion efficiency
D
Independent variable: $\text{TiO}_2$ layer thickness; Dependent variable: Ambient temperature

Answer

The independent variable is the

\text{TiO}_2

layer thickness, and the dependent variable is the power conversion efficiency.

The researchers deliberately changed the thickness of the

\text{TiO}_2

electron-transport layer (

50\text{ nm}

200\text{ nm}

) across experimental conditions, making layer thickness the independent variable. The resulting power conversion efficiency was measured to assess solar cell performance, making efficiency the dependent variable.

Step-by-Step Solution

Identify the factor systematically altered by the experimenters across trials.

The researchers intentionally varied the

\text{TiO}_2

layer thickness between four values (

50\text{ nm}

100\text{ nm}

150\text{ nm}

, and

200\text{ nm}

). This is the independent variable.

The independent variable is the condition or factor directly manipulated in an experiment to test its effect.

Identify the factor being measured as a response to the experimental manipulation.

The researchers observed and measured the resulting power conversion efficiency for each solar cell sample. This is the dependent variable.

The dependent variable is the performance outcome or response variable measured during the study.

Distinguish independent and dependent variables from controlled experimental factors.

Factors such as light intensity (

1,000\text{ W/m}^2

) and operating temperature (

25^\circ\text{C}

) were kept fixed across all samples, identifying them as controlled variables.

Controlled variables must be maintained constant so that observed changes in the dependent variable can be attributed solely to the independent variable.

Key Concept

Identifying Independent, Dependent, and Controlled Variables

Estimated Time:1m 0s

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic