Current. A charge in an electric field is subject to a force. Acceleration Positive charges move with the field. Negative charges move against the field. -. +. Moving Charge. E. Moving water in a pipe forms a current. Steady flow at constant velocity
Positive charges move with the field.
Negative charges move against the field.
Steady flow at constant velocity
The mass flow is the density times velocity times area.
Pressure provides the force.Water Flow
Charge density ne instead of mass density
The charge flow is the density times velocity times area.
Defined for positive charge
Potential provides the force.
Collide with other charges
A potential along a wire causes a net velocity for electrons.
Negative charge moves opposite to currentCurrent Direction
I = Dq/Dt
(3.20 x 10-6 C)/(200 x 10-3 s)
I = -16.0 mA (negative beam)
The charge of one electron is used to get the number rate.
(-1.60 x 10-5)/(-1.60 x 10-19)
De/Dt = 1.00 x 1014 electrons/s
In an electron microscope a constant electron beam transports 3.20 mC of electrons in 200 ms across a vacuum.
Find the current and number of electrons per second.Electron Beam