Electricity and Static Electricity Flashcards
Current definition
Rate of flow of electric charge
ampere, A
Potential difference definition
how much energy is transferred between two points in a circuit
1V equivalent to 1J/C
resistance definition
how much a component decreases the current
charge definition
unit carrying electrical energy (Coulomb, C)
Why resistance increases with temperature
Electrons collide with ions in lattice they flow through
This causes them to vibrate and heat up
Transfers electrical energy to heat energy
Why resistance decreases current
More ions vibrate in the lattice the electrons go through, making it harder for the electrons to go through
Ammeter function
Measures current
Must be placed in series with component
Voltmeter function
Measures potential difference
Must be placed in parallel with component
Diode facts
Only lets current go in one direction
Thermistor facts
keeping supply potential difference constant gradually heats it
As temperature increases, current through thermistor increases (resistance decreases)
Useful in electronic thermostats
LDR facts
light-dependent resistor
as light level near it increases, current increases as resistance decreases
Useful in automatic night lights and burglar detectors
I-V graph of resistors and wires
Current is directly proportional to potential difference
Straight line
I-V graph of filament lamp
Increasing current increases temperature of filament, so resistance increases, causing curve
S-shape
I-V graph of diode
Current is only allowed to flow in one direction
Diode has high resistance in opposite direction
Straight horizontal line then increasing curved line
Series circuit facts
All components must be connected or whole circuit fails
Components are connected end-to-end between +ve and -ve of power supply
Total potential difference is shared between components
Total resistance increases as more components increase
Current is the same everywhere
Parallel circuits facts
Each component is connected separately to +ve and -ve of power supply
Disconnecting one component hardly affects others at all
Potential difference is the same across all components
Current is shared between branches
Total current in is equal to total current out
Total resistance decreases as you add more components in parallel
Fuse function
Uses heat created by resistance in circuit to break the circuit when it gets too hot (current gets too high)
How filament bulbs, toasters and electric heaters work
Contains as coil of really high resistance
Causes lots of thermal energy to be emitted, causing a glowing effect