Current Graphs — Slope and Area
Three graphs on draggable axes, all saying the same thing. The slope of a Q–t line is the current, the slope of an N–t line is the current divided by e, and the area under an I–t curve is the charge that has passed.
Como usar esta simulação
- Choose Q against t and drag the line to change its gradient
- Choose N against t to see the same relationship counted in electrons
- Choose I against t and shade an interval to read off the charge
- Bend the I–t curve to check that the area still gives the charge when I is not constant
O que observar
- A steeper Q–t line means a larger current, and a horizontal one means no current at all
- The N–t gradient is the Q–t gradient divided by e — the same graph in different units
- A rectangular I–t block gives Q = It, the constant-current special case
- A sloping or curved I–t graph still gives the charge as its area, where Q = It would fail
- A negative I–t region subtracts area, meaning charge flowing back the other way
A física por trás
Current is the rate of flow of charge, I = ΔQ/Δt, so on a Q–t graph the current is the gradient and a straight line means a steady current. Because charge is quantised as Q = Ne, an N–t graph is the same shape scaled by e and its gradient is I/e — the number of carriers per second. Reading the definition the other way, the charge transferred between two times is the area under the I–t curve in that interval, whether or not the current was constant.