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What is electric current, and how is it different from voltage?

What is electric current? It is the net flow of electric charge through a conductor. The quiz covers current vs voltage, why metals make good electrical conductors, the unit of current, potential difference, direct current, and what happens when a switch opens a circuit. Try the ten questions now.

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Question 1

What does electric current measure?

Current is charge flow per unit time.

Source excerpt
This measurement of how much charge flows past a point in a certain amount of time is the rate of flow.

From the Knowverse course text.

Question 2

Which particles carry current through a metal wire?

Mobile electrons carry charge through a metal. Its atomic nuclei remain in place.

Source excerpt
An electron is a tiny particle that carries a negative electric charge.

From the Knowverse course text.

Question 3

Why do metals function effectively as electrical conductors?

Metals contain free electrons that are not bound to individual atoms, allowing electric charge to pass through with little resistance.

Source excerpt
Free electrons are specific electrons that are not stuck to any single atom and can move around easily.

From the Knowverse course text.

Question 4

What is the standard unit used to measure electric current?

Current measures the rate of charge flow past a point in a given timeframe, expressed in Amperes.

Source excerpt
Because counting trillions of individual charges would be impossible, we use a standard unit called the Ampere.

From the Knowverse course text.

Question 5

In a simple battery circuit, how does conventional current through the external circuit compare with electron drift?

Conventional current follows the positive-charge direction. In metal wires, negatively charged electrons drift the other way.

Source excerpt
Even though we know electrons move the other way, the math works perfectly using the positive-to-negative convention.

From the Knowverse course text.

Question 6

What does voltage between two points describe?

Voltage compares electric potential at two points and is measured in volts. It is energy per unit charge, rather than total energy.

Source excerpt
Electric potential energy is the total energy stored by a charge, while voltage is the potential energy *per unit* of charge.

From the Knowverse course text.

Question 7

What is the purpose of the plastic coating around a conducting wire?

Plastic is an insulator. It strongly resists charge flow and helps keep conducting parts separated.

Source excerpt
Materials that block this movement, like the plastic on your charging cable, are called insulators.

From the Knowverse course text.

Question 8

What happens when electric charge moves through a working load like a bulb?

A bulb transfers electrical energy into other forms. Charge continues around the circuit.

Source excerpt
In a potential drop, the energy is transformed into other forms like heat, light, or mechanical motion.

From the Knowverse course text.

Question 9

Which feature defines direct current?

DC is unidirectional. Its magnitude can vary, and it can be interrupted by a switch.

Source excerpt
When electric charge moves through a path without ever turning back or changing its course, we call it Direct Current.

From the Knowverse course text.

Question 10

What happens when a switch opens the only path in a simple battery-and-bulb circuit?

Opening the switch breaks the conducting loop, so the simple circuit cannot sustain current through the bulb.

Source excerpt
This broken, incomplete path is known as an open circuit.

From the Knowverse course text.

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Read more about the topic

Moving charge and conductive paths

Electric current is the net flow of electric charge. In a metal wire, electrons carry that charge, while the wire's atomic nuclei stay in place. Current measures how much charge passes a point per second. Its unit is the ampere, so a larger current means a greater rate of charge flow.

Metal conductors contain electrons that can move through the material. Plastic insulation strongly resists charge flow and helps separate the conducting wire from its surroundings. Conventional current uses the direction a positive charge would move. In a metal, electron drift runs in the opposite direction to that convention.

Source excerpt
A conductor is any material that allows electric charge to move through it with almost no resistance.

From the Knowverse course text.

Visualizing Electrons — image from Wikimedia Commons
Cyclotron motion wider view · Marcin Białek · CC BY-SA 4.0

Voltage, potential drops, and circuits

Voltage is the difference in electric potential between two points: a difference in potential energy per unit charge. A battery supplies energy to a circuit. As charge passes through a load such as a lamp, electrical energy transfers into light and heat. The voltage across that load describes energy transferred per unit charge.

A simple battery circuit needs a complete conducting loop through the load and back to the battery. Opening its switch breaks that path and stops sustained current. Direct current flows in one direction when it flows. Its magnitude can change, and switching it off does not make it alternating current.

Source excerpt
A circuit is a complete path that allows energy to travel from a source, through a device, and back to the source.

From the Knowverse course text.

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Sources

Sources: Electric Current and Potential. Each question or step includes an excerpt from the course.