Electricity and Circuits — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. Connecting two batteries end to end in a series increases the total voltage available to the circuit.
Placing batteries end to end adds their voltages together -- two 1.5-volt batteries in series give 3 volts total, providing a stronger push for the current.
2. A longer wire has more resistance than a shorter wire of the same thickness.
Electrons bump into more atoms as they travel through a longer wire, which creates more resistance and slows the flow of current compared to a shorter wire.
3. The symbol for a battery in a circuit diagram shows a long line for positive and a short line for negative.
In circuit diagrams, the battery symbol uses a long thin line for the positive terminal and a short thick line for the negative terminal, making it easy to identify each end.
4. A dimmer switch works by changing the amount of current flowing to a light bulb.
A dimmer switch adjusts how much current reaches the bulb -- less current means the filament glows dimly, and more current makes it glow brightly.
5. Silver is the best conductor of electricity, but copper is used more often because it costs less.
Although silver conducts electricity slightly better, copper is much cheaper and still an excellent conductor, making it the practical choice for wiring in homes and electronics.
6. A rechargeable battery can reverse its chemical reaction to store energy again.
When you plug in a rechargeable battery, electricity flows backward through it and reverses the chemical reaction, restoring the chemicals so they can produce electricity again.
7. In a circuit diagram, a straight line represents a wire.
Circuit diagrams use simple straight lines to represent wires because wires just carry current from one component to another without changing it.
8. Electrical resistance is the ability of a material to oppose the flow of current.
Resistance measures how much a material fights the flow of electrons. High-resistance materials like rubber barely let current through, while low-resistance materials like copper let it flow easily.
9. A fuse is a safety device that contains a thin strip of metal that melts if too much current flows.
A fuse contains a thin metal strip designed to melt when current gets dangerously high, which breaks the circuit and prevents wires from overheating and starting a fire.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
voltage
→ the push that moves electricity through a circuit
drawing that uses symbols to show a circuit
current
→ the flow of electrons through a conductor
the flow of electrons through a conductor
resistance
→ a force that opposes the flow of current
the push that moves electricity through a circuit
circuit diagram
→ drawing that uses symbols to show a circuit
a force that opposes the flow of current
Correct matches: voltage → the push that moves electricity through a circuit; current → the flow of electrons through a conductor; resistance → a force that opposes the flow of current; circuit diagram → drawing that uses symbols to show a circuit.