An electric field is an area where a charged particle will experience a force.
Charges with the same polarity repel, and charges with opposite polarities attract.
A charged object of any polarity will attract an uncharged object, due to the movement of electrons in the uncharged object. Objects with more free-moving electrons will create a stronger attraction.
Electric Field Diagrams
An electric field diagram shows the influence of charged objects on an electric field. Field lines show the path which a positive test charge, and more field lines signifies a stronger electric field.
- Field lines not making contact with charges
- Incorrectly labelled arrows
- Field lines touching each other
- Uneven spacing of field lines around charges
- Field lines not perpendicular to charges
When a charged particle is in an electric field, it will experience a force which gives it the potential to move. When a charged particle moves in an electric field, its potential changes as well. This is called potential difference (p.d.) or voltage.
Voltage is the work done per coulomb of charge.
is the work done (energy), in joules. is the charge, in coulombs. is the potential difference or voltage, in volts.
Energy is sometimes measured in electronvolts instead of joules, usually when talking about very small amounts of energy relevant to charged particles. One electronvolt is one volt times the charge of an electron, about
An electron gun is a device with an anode and heated cathode, with a high voltage across them. This causes electrons to leave the cathode and accelerate very rapidly towards the anode, firing the electron out of the device.
The speed of the fired electrons can be calculated using the kinetic energy formula,