QCM : Fundamentals of Electric Charge and Circuits — 10 questions

Questions et réponses du QCM

1. What does electric charge refer to in physics?

A property of matter that causes objects to experience electric forces
The resistance encountered by current in a circuit
The energy stored in an electric field
The flow of electrons through a conductor

A property of matter that causes objects to experience electric forces

Explication

Electric charge is a fundamental property of particles like protons and electrons that causes objects to attract or repel each other through electric forces. It is not the flow of electrons (which is current), nor energy stored in fields, nor resistance in a circuit.

2. What is the approximate mass of an electron?

1.67 x 10^-27 kg
9.11 x 10^-31 kg
1.67 x 10^-27 kg
9.11 x 10^-31 kg

9.11 x 10^-31 kg

Explication

The mass of an electron is approximately 9.11 x 10^-31 kg, which is much smaller than the mass of protons and neutrons, about 1.67 x 10^-27 kg. This specific value is explicitly stated in the content, making it the correct answer.

3. What is the role of charging by rubbing in the context of static electricity?

To transfer electrons between objects, creating an electric charge imbalance
To produce current flow in electrical circuits
To generate magnetic fields in conductive materials
To neutralize charges on objects and prevent static buildup

To transfer electrons between objects, creating an electric charge imbalance

Explication

Charging by rubbing involves transferring electrons from one material to another, which creates an imbalance of electric charge, leading to static electricity. This process is fundamental in generating static charges and phenomena such as sparks or attraction between objects.

4. When was Coulomb's law, which describes electric forces, published or established?

1850
1785
1820
1775

1785

Explication

Coulomb's law was formulated by Charles-Augustin de Coulomb in 1785, establishing the quantitative description of electric forces between charges. The other dates are either too early or too late relative to this key scientific milestone.

5. How do conductors and insulators differ in their ability to allow electric charge to move through them?

Conductors are transparent, while insulators are opaque.
Conductors are always metals, while insulators are always non-metals.
Conductors are better at conducting heat, while insulators are better at conducting electricity.
Conductors contain free moving charged particles, while insulators do not.

Conductors contain free moving charged particles, while insulators do not.

Explication

Conductors contain free moving charged particles, such as electrons, which enable easy flow of charge, whereas insulators lack such free particles, preventing charge movement.

6. Who is credited with defining electric current as the flow of charge and establishing the SI unit 'ampere'?

André-Marie Ampère
Michael Faraday
Charles-Augustin de Coulomb
Alessandro Volta

André-Marie Ampère

Explication

André-Marie Ampère is credited with defining electric current as the flow of charge and for establishing the SI unit 'ampere'. Coulomb is known for Coulomb's law, Faraday for electromagnetic induction, and Volta for the voltaic pile (battery).

7. What is the effect of a potential difference in an electric circuit?

It increases the resistance of the circuit.
It causes electric current to flow.
It prevents the flow of charge.
It decreases the voltage across the circuit.

It causes electric current to flow.

Explication

A potential difference causes electric current to flow in a circuit by providing the energy needed for charge to move. The other options are incorrect: potential difference does not directly increase resistance, decrease voltage, or prevent charge flow.

8. In a practical electrical circuit, which device should be used to measure the electric current flowing through a component?

Use a power supply to determine the current flow
Use a voltmeter connected in parallel across the component
Use a resistor to measure the current directly
Use an ammeter connected in series with the component

Use an ammeter connected in series with the component

Explication

An ammeter must be connected in series with the component to accurately measure the electric current flowing through it. Voltmeters are connected in parallel to measure potential difference, resistors do not measure current directly, and power supplies do not measure current.

9. What is a key feature of how voltmeters and ammeters must be connected in an electric circuit?

Both voltmeters and ammeters are connected in series.
Voltmeters are connected in series, and ammeters are connected in parallel.
Voltmeters are connected in parallel, and ammeters are connected in series.
Both voltmeters and ammeters are connected in parallel.

Voltmeters are connected in parallel, and ammeters are connected in series.

Explication

Voltmeters are designed to measure potential difference and must be connected in parallel to the component whose voltage is being measured, to avoid altering the circuit. Ammeters measure current and must be connected in series to measure the flow of charge through a component. Proper connection ensures accurate readings and circuit safety.

10. What is a fuse in electrical safety devices?

A switch that manually disconnects the circuit during maintenance
A device that regulates voltage to protect appliances
A device that melts when high current flows through it to prevent overheating
A device that automatically turns off the power supply when a fault occurs

A device that melts when high current flows through it to prevent overheating

Explication

A fuse is a safety device consisting of a thin metal wire that melts when high current flows through it, thereby disconnecting the circuit and preventing overheating and potential fires.

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Electric charge — definition?

A property causing electric forces between objects.

Positive vs negative charge — difference?

Positive from protons, negative from electrons.

SI unit of charge?

Coulomb (C).

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