Cambridge Lower Secondary Stage 7 Physics Flashcards

In the simple model of electricity, what is flowing around a complete circuit?

Topic: Electron flow
Answer: Electrons flow around the circuit through the conducting parts.

Why must a circuit be complete before a lamp can light?

Topic: Electron flow
Answer: Electrons need an unbroken path from one side of the cell, through the components, and back to the other side.

A wire is disconnected at one point. What happens to electron flow in the circuit?

Topic: Electron flow
Answer: The path is broken, so electrons cannot flow around the whole circuit and the current stops.

Why does a cell not 'send out electricity' into an open gap?

Topic: Electron flow
Answer: Electrons can only keep flowing when there is a complete conducting loop.

What role does a cell have in the simple electron-flow model?

Topic: Electron flow
Answer: The cell provides the push that makes electrons flow around the circuit.

A student says, 'The lamp uses up all the electrons.' Correct this idea.

Topic: Electron flow
Answer: Electrons are not used up by the lamp; they flow through components and continue around the circuit.

Why does a lamp glow when electrons flow through it?

Topic: Electron flow
Answer: The moving electrons transfer energy to the lamp, which changes some of that energy into light and thermal energy.

In a working series circuit, do electrons only move before the lamp or all around the circuit?

Topic: Electron flow
Answer: Electrons flow all around the complete circuit, including through the lamp and wires.

Why is a switch useful in a circuit?

Topic: Electron flow
Answer: It can close the gap to allow electron flow or open the gap to stop electron flow.

A switch is closed but the lamp still does not light. Give one circuit explanation.

Topic: Electron flow
Answer: There may still be another break, a missing cell, a dead cell, or a component connected incorrectly.

Why can a buzzer sound only when it is part of a complete circuit?

Topic: Electron flow
Answer: A buzzer needs electron flow through it to transfer electrical energy into sound.

What is wrong with saying that current starts at the cell and slowly reaches the lamp one electron at a time?

Topic: Electron flow
Answer: In a complete circuit, electrons already in the conductors begin moving around the circuit when the cell provides a push.

Why is a wire needed between components in a circuit diagram and in the real circuit?

Topic: Electron flow
Answer: The wire provides a conducting path that allows electrons to flow between components.

What happens to electron flow when a switch changes from closed to open?

Topic: Electron flow
Answer: The circuit path is broken, so electron flow around the whole circuit stops.

Why is the word 'flow' useful when describing electricity?

Topic: Electron flow
Answer: It helps describe electrons moving around the circuit, rather than electricity being a substance stored in one component.

A lamp is connected to one side of a cell only. Why will it not light?

Topic: Electron flow
Answer: There is no complete path back to the other side of the cell, so electrons cannot flow around the circuit.

What does a steady current in a simple circuit suggest about the electrons?

Topic: Electron flow
Answer: Electrons are flowing continuously around the complete circuit.

Why does adding a component anywhere in a series circuit affect the whole circuit?

Topic: Electron flow
Answer: All components share the same single path, so any change to the path affects electron flow through every part.

What is an electrical conductor?

Topic: Conductors and insulators
Answer: A substance that allows electrons to flow through it easily.

What is an electrical insulator?

Topic: Conductors and insulators
Answer: A substance that inhibits or prevents electron flow.

Why are metals commonly used for wires in circuits?

Topic: Conductors and insulators
Answer: Metals are good electrical conductors, so they allow electrons to flow easily.

Why is plastic commonly used around the outside of electrical wires?

Topic: Conductors and insulators
Answer: Plastic is an insulator, so it helps stop electrons flowing into places where they could be dangerous.

A test material is placed in a simple circuit and the lamp lights brightly. What does this suggest?

Topic: Conductors and insulators
Answer: The material is a good conductor because it allows electron flow.

A test material is placed in a circuit and the lamp does not light. What is the most likely conclusion?

Topic: Conductors and insulators
Answer: The material is an insulator or a very poor conductor, so it does not allow enough electron flow.