Topic 5- Electricity And Circuits Flashcards
Current
The rate of flow of charge.
What will a component need for a current to flow through it?
Needs a potential difference and complete circuit
Potential difference
Energy transferred per coulomb of charge that passes between 2 points in an electrical circuit.
Current units
Amperes (A)
Potential difference units
Volts (V)
Resistance
Anything that slows the current(flow) down
Unit of resistance
Ohm
2 things current depends on
Potential difference
Resistance
Charge formula
Current*time
Volt
One joule per coulomb
What causes current in metals?
Flow of electrons
Q=
IT
E=
QV
Energy transferred
Charge moved * potential difference
1 volt
1 joule per coulomb
V=
IR
Potential difference
Current * resistance
What can you use to change the current?
A variable resistor
What does charge have to work against?
What does this cause? What’s the side effect of this? Why?
Charge has to work against resistance, causing electrical transfer. This can be a useful transfer pr can be dissipated to thermal energy stores/surroundings. This is because the electrons collide w ions in the lattice , giving them energy to vibrate and heat up.
What happens as the resistor heats up in a given pd?
The current decreases
*with exception of thermistor which increases current as it heats up
What is an ammeter? Where does it go in a circuit?
A component used to measure current (amps), is placed in SERIES w the component.
What’s a voltmeter? Where do you place it in a circuit?
A component used to measure potential difference, is placed in PARALLEL to a component.
What’s an IV graph?
A graph used to show current against potential difference.
What does the IV graph of a resistor show?
That current is directly proportional to potential difference (linear graph).
How do you work out the resistance from an IV graph?
Resistance= 1/gradient
What does the IV graph of a filament lamp look like?
Curved as increasing current = increasing temp of filament
What does the IV graph of a diode look like?
Shows a non-linear graph only increasing on one side of graph as diode has high resistance in opposite direction.
What’s the relationship between lights nd resistance in an LDR (Light dependent Resistor)
As light dims, resistance increases
Dim = highest resistance
Bright= lowest resistance