Electricity Flashcards
(13 cards)
Disadvantages of series circuits
If one bulb/component fails all turn off
Advantages of series circuits
less likely to overheat;
circuit is simpler/uses fewer wires
lower voltage bulbs
all bulbs controlled with one switch
Why does a coil of wire heat up when there is current in it?
Coil has resistance
Electrons transfer/lose energy as they flow through the coil
Due to electron collisions with lattice ions in the coil
Define current
Rate of flow of charge
Describe current, voltage and resistance in series circuits
Current is the same everywhere
Total voltage of supply is shared between components (and depends on resistance of each component)
Total resistance is the sum of resistance of each component
Describe current, voltage and resistance in parallel circuits
Current is shared between branches. Total current is equal to total of currents through the separate components.
Current through a branch depends on the resistance of the branch. Higher resistance reduces current in branch.
Voltage is same across all branches
Total resistance of circuit decreases if you add a second resistor in parallel.
Describe effect of light on LDR
In bright light, resistance falls
In darkness, resistance increases
Describe effect of temperature on thermistor
In hot conditions, resistance drops
In cold conditions, resistance goes up
Voltage definition
Energy transferred per unit charge passed
Describe current-voltage graph for a wire
Proportional
Straight line through the origin
Describe current-voltage graph for
metal filament lamp
As voltage increases, current increases, temp of metal filament increases and resistance increases
S-shaped graph
Describe current-voltage graph for
diode
Current only flows through a diode in one direction
Horizontal line along x axis until positive then increases to almost vertical straight line
How to tell what resistance is from current-voltage graph
Flatter line/lower gradient means very high resistance
Steep line means low resistance
