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 series circuit gives electricity many different paths to travel through.
Corrected: A series circuit gives electricity only one path to travel through; a parallel circuit provides many different paths.
A series circuit has only one loop for electricity to follow, so all devices share the same path. A parallel circuit is the one that splits into many separate paths.
2. Fix the sentence:
Aluminum foil is an insulator, so it should never be used to connect parts of a circuit.
Corrected: Aluminum foil is a conductor that allows electricity to flow, so it can be used to connect parts of a simple circuit.
Aluminum is a metal, and metals are conductors because their electrons move freely. That is why aluminum foil lets electricity pass through it and can connect circuit parts.
3. Fix the sentence:
When a battery runs out of energy, it means the wires inside the battery have broken apart.
Corrected: When a battery runs out of energy, it means the chemicals inside the battery have been used up and can no longer produce electricity.
Batteries produce electricity through chemical reactions, not wires. When those chemicals are fully used up, the reaction stops and the battery can no longer push current through a circuit.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. The two ends of a battery are marked with a plus sign and a minus sign.
A battery has two terminals: the positive (+) end and the negative (minus, -) end. This difference in charge is what pushes electrons through a circuit.
2. A filament is a thin wire inside a light bulb that glows when electricity passes through it.
The filament is a very thin coiled wire that resists the flow of electricity, which causes it to heat up so much that it glows and produces light.
3. Objects with opposite electrical charges attract each other.
Opposite charges pull toward each other -- a positively charged object and a negatively charged object attract because their unlike charges create a pulling force.
4. A doorbell uses electricity to make sound energy.
When you press a doorbell button, electricity flows to a small speaker or striker that vibrates, converting electrical energy into sound energy so people inside can hear it.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. Why do batteries have a positive end and a negative end?
Sample answer: Batteries need a positive and negative end to create a difference in charge. This difference pushes electrons through the circuit from the negative terminal to the positive terminal, making electricity flow.
The positive and negative ends create a difference in charge called voltage. This voltage acts like a push that drives electrons from the negative terminal through the circuit to the positive terminal.
2. Give two examples of devices in your home that use electricity and name the type of energy each device produces.
Sample answer: A lamp uses electricity to produce light energy. A toaster uses electricity to produce heat energy. Both devices convert electrical energy into other useful forms.
A lamp converts electrical energy into light energy, and a toaster converts electrical energy into heat energy. Both examples show how electricity changes into the specific form of energy each device needs.