Evaluating Models & Explanations Practice Test

PASSAGE VII

PHYSICS: Data Representation

Introduction

A student investigated the relationship between voltage ($V$), current ($I$), and resistance ($R$) in a simple direct current (DC) electrical circuit.

•Voltage ($V$) is the electrical potential difference provided by a power source, measured in volts (V).

•Current ($I$) is the rate of flow of electrical charge, measured in amperes (A).

•Resistance ($R$) is the opposition to the flow of charge, measured in ohms ($\Omega$).

The student set up a circuit containing a variable voltage power supply, a resistor, and an ammeter (a device used to measure current).

Experiment 1

In the first experiment, the student used a resistor with a constant resistance of $10.0 \ \Omega$. The student varied the voltage supplied to the circuit from 2.0 V to 10.0 V and recorded the resulting current measured by the ammeter. Results are shown in Table 1.

Experiment 2

In the second experiment, the student set the power supply to provide a constant voltage of $12.0 \text{ V}$. The student then swapped out the resistor, testing five different resistors with varying resistance values, and recorded the resulting current for each. Results are shown in Table 2.

PASSAGE II

BIOLOGY: Research Summary

Soil salinity (salt concentration) and pH can significantly affect seed germination. A botanist conducted two studies to determine how these factors influence the germination rate of Medicago sativa (alfalfa) seeds. •Note: Germination rate is the percentage of planted seeds that successfully sprout.

Study 1

The botanist prepared 5 identical planting trays. Each tray was filled with 1 kilogram (kg) of the same potting soil. The botanist adjusted the soil in each tray to have a different concentration of sodium chloride (NaCl), measured in millimoles per kilogram (mM/kg). The soil pH for all trays was kept constant at 6.5.

Fifty M. sativa seeds were planted in each tray. The trays were placed in a greenhouse with a constant temperature of $25^\circ\text{C}$ and watered equally every day for 14 days. On day 14, the germination rate was recorded. Results are shown in Table 1.

Study 2

The botanist prepared 5 new trays with the same potting soil. This time, the NaCl concentration in all trays was kept constant at 40 mM/kg. The botanist adjusted the soil pH in each tray to a different value, ranging from highly acidic to highly basic.

Fifty M. sativa seeds were planted in each tray. The greenhouse conditions, watering schedule, and duration were identical to those in Study 1. Results are shown in Table 2.