Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Electrical conductivity is the property of a material to allow electric current to flow through it. Metals are generally excellent conductors of electricity.
Metals like Silver (), Copper (), and Aluminum () are widely used because they contain free electrons that act as charge carriers.
Silver () is the best conductor of electricity, but Copper () is more commonly used in household wiring due to its cost-effectiveness.
Most non-metals are insulators (poor conductors) because they lack free electrons. Examples include Sulfur () and Phosphorus ().
Graphite, an allotrope of the non-metal Carbon (), is a notable exception as it is a good conductor of electricity.
Electrical wires are typically coated with insulators like Polyvinyl Chloride (PVC) or rubber to prevent electric shocks.
📐Formulae
💡Examples
Problem 1:
Why is Copper () preferred over Silver () for making electrical wires even though Silver is a better conductor?
Solution:
Copper is preferred because it is significantly cheaper and more abundant than Silver.
Explanation:
While Silver () has the highest electrical conductivity, its high cost makes it impractical for large-scale use. Copper () provides a high level of conductivity () at a much lower price point.
Problem 2:
A circuit is broken by a gap. Which of the following materials will complete the circuit and make the bulb glow: a piece of wood, a plastic scale, or a graphite pencil lead?
Solution:
The graphite pencil lead.
Explanation:
Wood and plastic are non-metals and insulators. Graphite is a form of Carbon () that possesses free electrons, allowing it to conduct electricity and complete the circuit.
Problem 3:
If the resistance () in a wire is doubled while keeping the Voltage () constant, what happens to the current ()?
Solution:
The current () becomes half of its original value.
Explanation:
According to the formula , the current is inversely proportional to the resistance. If increases to , then the new current .