Topic P2 - Electricity Flashcards
Current definition
Flow of electrical charge
What is current measured in?
Ampere, A
Potential difference definition
Driving force that pushed charge round
What is potential difference measured in?
Volt, V
Resistance definition
Anything that slows down charge flow
What is resistance measured in?
Ohm, Ω
Current through a component depends on two factors:
1)
The component’s resistance
- The greater the resistance, the smaller the current.
2)
The potential difference across the component.
- The greater the potential difference, the larger the current (for a fixed resistance).
Size of current = rate of…
Size of current = rate of flow of charge
Charge flow formula
Q = It
Q - charge flow (C)
I - current (A)
t - time (s)
What is charge flow measured in?
Coulombs, C
Potential difference equation
V = IR
V - Potential Difference (V)
I - Current (A)
R - Resistance (Ω)
For circuit symbols look at page 83.
For circuit symbols look at page 83.
What are the 3 different I-V characteristics?
1) Ohmic conductors at constant temperature
2) Filament Lamp
3) Diode
I-V ohmic conductor at constant temperature graph characteristics
Current is directly proportional to potential difference so resistance doesn’t change.
Current is directly proportional to potential difference…
…so resistance doesn’t change
Is an ohmic conductor I-V graph liner or non-linear?
Linear
What are 4 examples of components with changing resistances when the current through them varies?
1) Filament Lamp
2) Diode
3) LDR
4) Thermistor
I-V, filament lamp graph characteristics
Current increase so temperature of filament increases so resistance increases.
I-V, diode graph characteristics.
High resistance in one direction so current only flows in the other direction.