Electricity and Circuits — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. A toaster converts electrical energy mainly into which form of energy?
A) sound energy
B) light energy
C) heat energy
D) chemical energy
A toaster uses electrical resistance to heat its coils, converting electrical energy to heat (and some light) energy.
2. Which safety device in a home is designed to prevent electrical fires?
A) light switch
B) extension cord
C) circuit breaker
D) power strip
A circuit breaker detects excess current and trips to open the circuit, preventing overheating and fires.
3. Two identical bulbs are connected in series to one battery. A third identical bulb is connected in parallel to the same battery by itself. Which bulb is brightest?
A) One of the series bulbs
B) They are all equally bright
C) The parallel bulb
D) None will light up
The parallel bulb gets the full battery voltage across it, while the series bulbs each get half. More voltage → more current → brighter.
4. What happens to the overall resistance when you add more bulbs in series?
A) Resistance decreases
B) Resistance stays the same
C) Resistance increases
D) Resistance disappears
In a series circuit, resistances add up. More bulbs = higher total resistance = less current = dimmer bulbs.
Part B: Fill in the Blank
Write the correct answer on each line.
1. A light bulb converts electrical energy into light and heat energy.
Light bulbs emit both light and heat as byproducts of electrical resistance in the filament.
2. The push that moves electrons through a circuit is called voltage.
Voltage (measured in volts) is the electrical pressure or potential difference that drives current through a circuit.
3. Resistance is measured in units called ohms.
The ohm (Ω) is the SI unit of electrical resistance, named after physicist Georg Simon Ohm.
4. A generator converts mechanical energy into electrical energy.
Generators use electromagnetic induction to convert mechanical motion (from turbines, engines, etc.) into electrical energy.
5. Power lines carry electricity at very high voltage over long distances.
Transmitting electricity at high voltage reduces energy loss over long distances. Transformers step it down before reaching homes.