electricty Flashcards
what is electric current
the flow of electrical charge
what does the current through a component depend on
- potential difference
- resistance
what is the trend in an ohmic conductor
- the current through an ohmic conductor (at constant temp) is directly proportional to the potential difference
- resistance remains constant
what is the trend in a filament lamp
- the resistance of a filament lamp increases as the temp of tincreases
what is the trend in a diode
- current only flows through one direction
- it has a very high resistance in the reverse direction
what is the resistance and LDR trend
- in light , the resistance of an LDR is very low - little energy needed for current to pass through - low PD
- in the dark , the resistance is very high - lots of energy needed - high PD
uses of LDRS
- automatic night lights
- burglar detectors
trends in resistance and thermistors
- in cold temps , the resistance is high - more energy needed for current to pass through a resistor - high PD
- in hot temps the resistance is very low , less energy needed for current to pass through thermistor - LOW PD
applications of thermistors
thermostats
what is an alternating current
- current is constantly changing direction
what is a direct current
a current that is always flowing in the same direction
What is the frequency & potential difference of the uk mains supply
Frequency : 50HZ
Potential Difference: 230V
what are the 3 wires
- live
- neutral
- earth
what colour is the live wire
brown
what colour is the neutral wire
blue
what colour is the earth wire
green and yellow
what does the neutral wire do
- completes the circuit
what is the potential difference of a neutral wire
0V
what does the live wire do
- provides alternating potential difference from the mains supply
what is the potential difference of the live wire
230V
what does the earth wire do
stops the appliance from becoming live
what is the potential difference of a earth wire
0V
