Electric Circuits Flashcards
Potential difference
the work done per unit positive charge.
V = W/Q
For a current to flow in an electric circuit we need
- a closed conducting path
- a source of electrical energy
- at least one energy converter
Current
the rate of flow of charge.
I = q/t
Ohm’s Law
current through a conductor is directly proportional to the potential difference across the conductor at constant temperature.
Ohmic and non-ohmic conductors
Ohmic - obeys ohms law
non-ohmic does not obey ohms law
Resistance
a material’s opposition to the flow of electric current.
Factors affecting resistance
- type of material
- length
- cross-sectional area (thickness)
Power and energy theory
Internal and external circuits
Internal - the source of electrical energy.
External - consists of all the electrical components connected to a source.
Potential difference in a battery
chemical reactions in the battery create an electric field inside the battery and provide energy to move charge against the field (charge flows + to - in ext, circuit, in battery moves from - to +).
moving charge against the field results in a gain of potential energy by the charge, so there is a “potential difference” across the terminals of the battery.
Internal resistance
resistance in battery.
Electromotive force (emf)
the total energy supplied per coulomb of charge by the cell.
Series circuits
emf = Vbatt = V1 + V2 + V3 +…
I total = I 1 = I 2 = I 3 =…
R total = R1 + R2 + R3 +…
Parallel circuits
emf = Vbatt = V1 = V2 = V3 =…
I total = I 1 + I 2 + I 3 +…
1/R total = 1/R1 + 1/R2 + 1/R3 +…
Connecting meters in circuits
Voltmeter - parallel
Ammeter - series
Ohmmeter - open circuit
