Grade 8 Physical Sciences Control Test Preparation

Flashcards reviewing key concepts for the Grade 8 Physical Sciences Control Test, including Scientific Skills, Static Electricity, Energy Transfer in Electrical Systems, and Series vs. Parallel Circuits.

What is an investigative question in scientific inquiry?

A clear question that asks about the relationship between two variables and must always end with a question mark.

What is a hypothesis and how is it typically structured?

An educated guess or prediction about the outcome of an experiment that states how the independent variable affects the dependent variable (e.g., 'If X increases, then Y will decrease').

What is the difference between an independent variable and a dependent variable?

An independent variable is the factor deliberately changed or manipulated in an experiment, whereas a dependent variable is the factor measured to see how it changes in response.

What are controlled (fixed) variables and why are they necessary?

Controlled variables are factors that must be kept exactly the same throughout the experiment to ensure a fair test.

What is the purpose of a conclusion in a scientific experiment?

It is a final statement summarizing what was learned, directly answering the investigative question, and stating whether the hypothesis was correct.

How are subatomic particles arranged in the structure of an atom?

Positive protons and neutral neutrons are fixed inside the central nucleus, while negative electrons orbit around the nucleus and are free to move.

What occurs at the particle level during charging by friction?

Friction transfers electrons from one material to another when two different neutral materials rub together. Protons never move.

How does gaining or losing electrons affect the net charge of an object?

Gaining electrons causes an object to become negatively charged, while losing electrons causes an object to become positively charged.

What are the two main laws of charge for electrostatic forces?

Like charges repel (positive pushes positive away; negative pushes negative away), and unlike (opposite) charges attract (positive and negative pull towards each other).

What causes lightning and what safety rules should be followed during a storm?

Lightning is a massive natural electrostatic discharge caused by friction between cloud particles. During a storm, always go indoors and stay away from water, tall trees, and metal structures.

How is energy transformed within an electrical circuit?

An electrical circuit transfers potential energy from a source (cell/battery) to other forms of energy via output devices (like bulbs or buzzers).

What is the heating effect of an electric current and what are its practical applications?

When electric current flows through a high-resistance wire (like nichrome or steel wool), it heats up. This is used in kettles, heaters, and incandescent light bulbs.

What is the magnetic effect of an electric current?

An electric current flowing through a coiled wire creates a magnetic field around it, forming an electromagnet.

What is the chemical effect (electrolysis) of an electric current?

Passing current through a chemical solution breaks down the compound into its elements (e.g., electrolysis of copper chloride).

What is resistance in an electrical circuit?

Resistance is the opposition to the flow of electric charge. High-resistance components slow down current and generate heat.

How do pathways and current behavior work in a series circuit?

There is only one path for current to flow, and the current $I$ is the same at all points ($I_{total} = I_1 = I_2$).

What happens when more resistors are added to a series circuit, or if one bulb breaks?

Adding more bulbs increases total resistance and decreases overall current (bulbs get dimmer). If one bulb breaks, the whole circuit stops working.

How do pathways and current behavior work in a parallel circuit?

There are multiple pathways (branches) for current to flow, and current $I$ splits across branches ($I_{total} = I_1 + I_2$).

What happens when more branches are added to a parallel circuit, or if one bulb breaks?

Adding more branches decreases total circuit resistance, which increases total current from the battery while bulbs maintain their brightness. If one branch breaks, the other branches keep working.