Brief P2 Flashcards
How draw Circuit symbol fr..
-I i-
+ -
How draw lamp
Circle with x fr
How draw fuse
Rectangle with line thru
How draw diode
Play button
How draw resistor
Rectangle
How draw thermistor
Ugly tick starting from bottom left
How draw variable resistor
Actual tik
Draw LDR
two ticks coming into a circle with a rectangle inside
Draw LED
tick bouncing off
Diode symbol
What is an ohmic conductor and state the conditions required
A Conductor for which current and potential difference are directly proportional
Resistance remains constant as current changes
Temperature must be constant
4 components for which resistance is not constant as current changes
Lamps
Diodes
Thermistors
LDR
What happens to resistance of a filament lamp as the temperature increases and why
(4 marks)
Resistance increases
Ions in metal have more energy so collide more frequently with electrons as they flow through the metal - creating greater resistance to current flow
What is different about current flow through a diode
Current flow in one direction
Resistance is very high in the other direction preventing current flow
What is different about current flow through a diode
Current flow in one direction
Resistance is very high in the other direction preventing current flow
Two examples of when a thermistor may be used
In a thermostat to turn a heater on below a certain temperature
In a freezer to turn on a cooler when the temperature becomes too high
What happens to the resistance of a LDR as light intensity decreases
LDR’s resistance increases
Give an application for a LDR
Street lights often use LDR
When light levels become too low, the light gains sufficient current to turn on
Function of brown wire
Live
Carries p.d from mains supply to appliance
P.d between life and earth 230V
Function of blue wire
Neutral
Completes the circuit
0V
Function of green and yellow wire
Earth
Only carries current if theres a fault
0V
What is meant by earthing
A safety device means earth wire joins the metal case
