How to Calculate Drift Velocity and Current Density in Conductors

TL;DR

To calculate drift velocity in a conductor, use the formula: drift velocity = current / (density of free electrons × charge of an electron × area). Current density is calculated as current divided by area. Drift speed is typically very low, and both drift speed and current density are directly related — changing the cross-sectional area impacts both variables inversely.

Transcript

in this video we're going to focus on solving some basic problems associated with the drift speed of an electron in a metal and also the current density so in this example we have a silver cylindrical conductor with a radius of one centimeter and it has a current of five amps flowing through it so let's draw a picture let's say this is the cylindri... Read More

Key Insights

• 😘 The drift speed of electrons in a conductor is very low compared to their random motion.
• 🐎 The drift speed and current density in a conductor are directly related.
• 😵 Changing the cross-sectional area of a conductor affects the drift speed and current density in opposite directions.
• 🐎 The time it takes for an electron to travel a distance depends on the drift speed and can be significant even for short distances.

Questions & Answers

Q: How can the drift velocity in a conductor be calculated?

The drift velocity can be calculated using the formula: drift velocity = current / (density of free electrons * charge of a single electron * cross-sectional area). Assign appropriate values to the variables and calculate the drift velocity.

Q: What is the relationship between the drift speed and current density in a conductor?

The drift speed and current density in a conductor are directly related. As the drift speed increases, the current density also increases.

Q: How does changing the cross-sectional area of a conductor affect the drift speed?

Decreasing the cross-sectional area of a conductor increases the drift speed, given that the current remains constant. This is due to the conservation of charge.

Q: How long does it take for an electron to travel a distance of one meter in a conductor?

The time it takes for an electron to travel one meter can be calculated using the formula: time = distance / drift speed. Assign the appropriate values and calculate the time.

Summary & Key Takeaways

• The video focuses on solving problems related to drift speed and current density in a silver cylindrical conductor with a given radius and current.

• The drift velocity in the conductor is calculated using the formula: drift velocity = current / (density of free electrons * charge of a single electron * cross-sectional area).

• The current density in the conductor is calculated using the formula: current density = current / area.

• The time it takes for an electron to travel a distance of one meter in the conductor is also calculated.