Electricity and Circuits — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. Which statement about parallel circuits is true?
A) All devices share one single path
B) If one device breaks, all others stop working
C) Each device has its own path for current
D) Adding more devices makes each one brighter
In a parallel circuit, each branch provides a separate path for current. This is why one device failing doesn't stop the others.
2. A student builds a circuit with a battery, wires, and a bulb, but the bulb does not light. What is the most likely problem?
A) The wires are too long
B) There is a gap in the circuit
C) The battery is too powerful
D) The bulb is too bright
If a circuit is incomplete (open), no current flows and the bulb won't light. A gap anywhere in the path breaks the circuit.
3. Which material would make the best wire for a circuit?
A) rubber
B) glass
C) copper
D) wood
Copper is an excellent conductor with low resistance, making it ideal for electrical wiring.
4. Why do the lights in your house stay on when one light bulb burns out?
A) The house uses very strong batteries
B) The lights are wired in a series circuit
C) The lights are wired in a parallel circuit
D) The burned-out bulb still conducts electricity
Home lighting is wired in parallel so each light has its own path. A burned-out bulb only opens that one branch.
Part B: Fill in the Blank
Write the correct answer on each line.
1. Electricity always follows the path of least resistance.
Ohm's Law: current naturally takes the easiest path (lowest resistance) through a circuit.
2. A short circuit happens when electricity takes an unintended path and can cause overheating.
A short circuit bypasses the intended load, allowing very high current to flow and potentially causing fires.
3. In a series circuit with three bulbs, removing one bulb creates an open circuit.
Removing a bulb from a series circuit creates a gap, opening the circuit and stopping all current flow.
4. Metals are good conductors because their outer electrons move freely.
Metals have 'free electrons' in their outer shells that can move easily, enabling electrical conduction.
5. The brightness of a bulb in a circuit depends on the amount of current flowing through it.
More current through a bulb filament means more energy converted to light and heat, producing greater brightness.