Electricity definitions Flashcards
circuit rule for current (Kirchhoff’s first law)
- The current passing through two or more components in series is the same through each component. 2. At a junction, the total current in = the total current out.
circuit rules for pd (Kirchhoff’s second law)
- For two or more components in series, the total pd across all the components is equal to the sum of the pds across each component. 2. The sum of the emfs round a complete loop in a circuit = the sum of the pds round the loop.
current
rate of flow of charge, the charge that passes a point per unit time
emf
energy gained per unit charge in the power supply
diode
a component that only allows current to flow in one direction through it
internal resistance
resistance inside a source of electrical energy; the loss of pd per unit current in the source when current passes through it.
light-dependent resistor
resistor which is designed to have a resistance that changes with light intensity. As light intensity increases, the resistance decreases.
negative temperature coefficient thermistor
a component whose resistance decreases when its temperature is increased
Ohm’s law
the pd across a metallic conductor is proportional to the current, provided the physical conditions do not change (e.g. temperature is constant)
potential difference
work done or energy transfer per unit charge between two points when charge moves from one point to the other
potential divider
two or more resistors in series connected to a source of pd
resistance
the ratio of potential difference across a component to the current through the component
resistivity
(resistance x cross-sectional area)/length
semiconductor
a substance in which the number of charge carriers increases when the temperature is raised.
superconductor
A material that has zero electrical resistance. Materials become superconductors at or below a critical temperature.
