Circuit Basics
What three basic components are needed to make a simple electric circuit work?
Answer: A source of electric energy, an electric device, and an electric conductor.
What electrical quantity describes the difference in electrical potential energy between two points in a circuit?
Voltage
What do we call the movement of electrically charged particles through a circuit?
electric current
You press the power button on a battery-operated flashlight, and the bulb turns on. What change in the circuit allows this to happen?
Answer: The switch closes the circuit, creating a complete path for electric current.
What is the difference between an open circuit and a closed circuit?
Answer: A closed circuit has a complete path that allows current to flow; an open circuit has a break in the path.
When electrical energy reaches a working light bulb, what two forms of energy can it produce?
Answer: Light energy and thermal (heat) energy.
A battery is connected to wires and a light bulb, but the circuit is left open. Will electric current flow continuously through the entire circuit? Explain why or why not.
No. The open circuit breaks the conducting path, preventing continuous current through the entire circuit.
A student builds a circuit with a battery and bulb. The bulb lights up, but the connecting wires also become slightly warm. What explains the warming of the wires?
Answer: Some electrical energy is converted into thermal energy in the wires.
What is the purpose of a switch in a simple circuit?
Answer: To open or close the circuit and control whether current flows.
Two identical light bulbs are each connected to a battery, one with a voltage of 3 V and the other with 6 V. According to the lesson, which bulb produces more light, and approximately how does their brightness compare?
Answer: The bulb connected to 6 V produces about twice as much light as the bulb connected to 3 V.
In a battery, at which terminal do negatively charged particles tend to concentrate?
the negative terminal
A toy car's motor runs weakly with one battery but runs more strongly when connected to a higher-voltage source designed for that motor. What is the best explanation?
Answer: The higher voltage can transfer more electrical energy per unit of charge, allowing more energy to be converted into other forms.
A _________________________ is a point where electricity enters or leaves an electrical device
electrical terminal
What does the voltage measured across a portion of a circuit indicate?
It indicates how much electrical energy is transferred per unit of charge across that portion of the circuit, or the electrical potential difference.
A student says that electrons disappear when they pass through a light bulb because the bulb uses them to make light. What is wrong with this explanation?
Answer: Electrons continue moving through the complete circuit; the bulb converts electrical energy into light and thermal energy rather than using up the electrons.
A student tests two circuits that differ only in their voltage sources. One circuit has a 1.5 V battery, and the other has a 9 V battery. What should the student measure or observe to investigate how voltage affects a bulb?
Answer: Compare the bulbs' brightness under the two voltage conditions, keeping the other circuit components the same.
A student connects a battery, wires, and a light bulb, but the bulb does not light because one wire is disconnected. What must the student do to allow current to flow?
Answer: Reconnect the wire to complete the circuit and create a closed path.
A battery powers a small motor. Explain what happens to the electrical energy as the motor operates.
Answer: Electrical energy is transformed into other forms, especially mechanical energy that turns the motor, with some energy also becoming thermal energy.
A battery continues its chemical reactions while connected to a complete circuit. What allows electric current to keep flowing?
Answer: The battery maintains an electrical potential difference, and the closed conducting path allows charged particles to move.
A student builds a circuit that lights a bulb and claims, “The battery sends energy to the bulb, so the electrons must travel from the battery and get used up inside the bulb.” Use what you know about electric current and energy transfer to correct the student's claim.
Answer: Charged particles move through the complete circuit, while energy is transferred from the battery to the bulb and converted into light and thermal energy. The electrons are not used up by the bulb.