Chapter 24, Problem 1FTD

Explain the difference between current and current density.

To determine

The difference between current and current density.

Answer to Problem 1FTD

Electric current is a scalar quantity and current density is a vector quantity. That is electric current has magnitude only but electric current density has both direction and magnitude and also electric current is the flow of charges but current density is the amount of current passing per unit area.

Explanation of Solution

Electric current is the time rate of flow of charges or ions. It is measured using the apparatus called ammeter and the unit of current is ampere. The magnitude of current depends on the potential difference and the resistance.

Write the equation to find the electric current.

$I=\frac{q}{t}$

Here,

$I$ is the current.

$q$ is the charge.

$t$ is the time.

The magnitude of current increases as the number of charges increases.

Write the equation to find the current density.

$J=\frac{I}{A}$

Here,

$J$ is the electric current density.

$I$ is the current.

$A$ is the area.

The current density can be explained as the amount of current passing through unit area. Current densities are denoted by the symbol $J$. It is a vector quantity and the direction is always perpendicular to the surface area under consideration. It’s value varies as the material of the conductor changes and it also depends on the temperature.

Conclusion:

Electric current is a scalar quantity and current density is a vector quantity. That is electric current has magnitude only but electric current density has both direction and magnitude and also electric current is the flow of charges but current density is the amount of current passing per unit area.