Controlling And Using Electric Current Flashcards
What is current
The rate of flow of charge around a circuit it will only flow if there is a voltage
What is voltage
The force that pushes the current around the circuit
What is resistance
Anything in the circuit that slows the flow down
How do voltage and resistance effect the current
If you increase the voltage more current will flow
If you increase the resistance less current will flow
What happens to current at a junction
Current is always conserved so the total entering a junction is equal to the total leaving the junction but it can split between the different pathways
What is a parallel circuit
Each component is separately connected to the positive and negative of the circuit
There are junctions where the current splits
What is the standard test circuit
There's A power A component A voltmeter A resistor An ammeter
The ammeter measures the current and is connected in series with the component
The voltmeter measures the potential difference and is connected in parallel with the component
What happens in a fixed resistor
A current through a resistor is proportional to voltage
Different resistors have different resistances but the graph will always be a straight line showing positive correlation
What happens in a filament lamp
As the temperature of the lamp increases the resistance increases giving a curve
The graph creates a stretched out “S” shape crossing at 0,0
What happens In a diode
Current will only flow through the diode in one direction so the graph goes along the X axis until it reaches 0 then curves upwards like s backwards C
Potential difference =
Current X resistance
What is a light dependant resistor
A resistor that has least resistance in the light and most resistance in the dark
What is a thermistor
There’s less resistance in hot conditions and more resistance in cold
What happens when’s a current passes through a resistor
There is an energy transfer that heats the resistor
This is because of the electrons colliding with the ions in the lattice that make up the resistor
The collisions give the lattice extra energy which is emitted as heat
Heating increases the resistance so less current will flow or a higher potential difference will be needed for the same current to flow
Electrical power =
Potential difference X current
Energy transferred =
Current X potential difference X time
