Electricity (AS) (AQA) Flashcards
Define current
Rate of flow of charge around a circuit
Give the unit of current
Amperes (A)
Define potential difference
Work done (energy transferred) per unit charge
State the unit of potential difference
Volts (V)
Describe current and potential difference in a series circuit
Current is the same in each component
Potential difference is split between the components
Describe current and potential difference in a parallel circuit
Potential difference is the same in each component
Sum of the currents through each component = total current (current is split)
Define resistance
Resistance = V/I
Define charge carriers
Charged particles that move through a substance when a potential difference is applied to it
What are the charge carriers in a metal?
Delocalised electrons
What are the charge carriers in a solution (eg salt solution)?
Charged ions
What is charge (Q) measured in?
Coulombs (C)
Define 1 coulomb
1 coulomb (C) is the amount of charge that passes in 1 second when the current is 1 ampere
Define conventional current
The relative direction in which positive charges/ions flow in a circuit
What is the direction of conventional current?
+ –> -
What is the direction of electron flow?
- –> +
Are anions attracted to the anode or cathode in electrolysis?
Anode (+)
State Kirchoff’s First Law
The sum of the current entering a junction = the sum of current leaving it
(Conservation of charge)
What are the advantages of parallel circuits?
Extra components can be added without affecting the output of the others
When one appliance breaks they don’t all fail
State ohm’s law
The current (I) in a conductor is proportional to the potential difference (V) across it provided temperature is constantly
What is the threshold voltage for a silicon diode and what does this mean?
Around 0.6V
This means that the diode conducts very easily in the forward direction above 0.6V, but very little below 0.6V or in the opposite direction
Explain the shape of an I-V graph for a filament lamp
The graph is a curve because as current increases temperature increases so resistance increases (so voltage increases)
Why is a resistor an ‘ohmic material’?
Because ohm’s law is obeyed (I is proportional to V, it is a straight line graph through the origin etc)
Give the unit for resistivity
The ohm metre
What is the defining characteristic of a superconductor?
The component has 0 resistivity/resistance
