4.1: Charge and current Flashcards
Conductors
A material that allows the flow of electrical charge. Good conductors have a large amount of free charge carriers to carry a current.
Conservation of charge
The total charge in a system can not change.
Conventional current
The flow from positive to negative, used to describe the direction of current in a circuit.
Coulomb
The unit of charge
Electric current
The rate of flow of charge in a circuit
Electrolytes
Substances that contain ions that when dissolved in a solution, act as charge carriers and allow current to flow.
Electron flow
The opposite direction to conventional current flow. Electrons flow from negative to positive.
Elementary charge
The smallest possible charge, equal to the charge of an electron.
Insulators
A material that has no free charge carriers and so doesn’t allow the flow of electrical charge.
Kirchhoff’s first law
A consequence of the conservation of charge. The total current entering a junction must equal the total current leaving it.
Mean drift velocity
The average velocity of an electron passing through an object. It is proportional to the current, and inversely proportional to the number of charge carriers and the cross sectional area of the object.
Quantization of charge
The idea that charge can only exist in discrete packets of multiples of the elementary charge.
Semiconductors
A material that has the ability to change its number of charge carriers, and so its ability to conduct electricity. Light dependent resistors and thermistors are both examples.
