Electricity and Circuits — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
A light switch works by keeping the circuit closed at all times so the light stays on.
Corrected: A light switch works by opening and closing the circuit; flipping it on closes the circuit so electricity flows and the light turns on.
The corrected sentence is: "A light switch works by opening and closing the circuit; flipping it on closes the circuit so electricity flows and the light turns on.". The original sentence "A light switch works by keeping the circuit closed at all times so the light stays on." contained an error that needed to be fixed.
2. Fix the sentence:
Wood and metal are both good conductors of electricity used in building circuits.
Corrected: Metal is a good conductor used in circuits, but wood is an insulator that does not let electricity flow easily.
The corrected sentence is: "Metal is a good conductor used in circuits, but wood is an insulator that does not let electricity flow easily.". The original sentence "Wood and metal are both good conductors of electricity used in building circuits." contained an error that needed to be fixed.
3. Fix the sentence:
Electricity flows through a circuit in both directions at the same time like water in a lake.
Corrected: In a simple direct-current circuit, electricity flows in one direction around the loop, from one terminal of the battery to the other.
The corrected sentence is: "In a simple direct-current circuit, electricity flows in one direction around the loop, from one terminal of the battery to the other.". The original sentence "Electricity flows through a circuit in both directions at the same time like water in a lake." contained an error that needed to be fixed.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. A switch is used to open and close a circuit.
A switch controls a circuit by completing or breaking the current's path, turning devices on or off.
2. Copper is used in wires because it is an excellent conductor.
Copper is one of the best electrical conductors and is used in most household wiring.
3. Plastic coating on wires is an insulator that keeps people safe.
Plastic insulation around copper wire prevents accidental shock by blocking current from reaching the outside.
4. The flow of electricity through a wire is called electric current.
Electric current is the rate at which electric charge (electrons) flows through a conductor, measured in amperes.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. Name three materials that are good conductors and three that are good insulators.
Sample answer: Good conductors include copper, aluminum, and iron. Good insulators include rubber, plastic, and glass. Conductors let electricity pass through while insulators block it.
Metals are generally good conductors because their electrons move freely. Non-metals like rubber, glass, and plastic are insulators.
2. Explain why a flashlight stops working when you remove one battery.
Sample answer: Removing a battery breaks the circuit and creates a gap. Electricity needs a complete loop to flow, so the bulb cannot light up without the full path from the batteries.
All circuit components must be connected in a continuous path. Removing a battery creates an open circuit.