electricity Flashcards
what is the formula for charge flow(c)?
current(A) x time(s)
what is the potential difference (voltage)?
the driving force that pushes the charge round
what is the formula linking potential difference(v)
Current(I) x resistance(R)
what is the unit of current?
Ampere
what is resistance?
anything that slows the flow down
what factors does the resistance of the circuit depend on?
- -> If component are in a series or parallel
- -> Length of wire used in circuit
At a constant temperature what is the current?
The current flowing through an ohmic conductor is directly proportional to the potential difference across it
what happens when an electrical charge flows through a filament lamp?
- -> transfers some energy to the thermal energy store of the filament lamp.
- ->designed to heat up resistance with temperature.
what are the i-v characteristic of linear components?
> Straight line e.g. fixed resistor
what are the i-v characteristic of non-linear components?
> Curved (e.g. lamp or diode)
what happens if a component is removed or disconnected?
The others will barely be affected
what is the light dependent resistor?
- -> A resistor dependent on light
- -> In darkness resistance is at its highest
- -> Resistance falls in bright light
what is the temperature dependent resistor?
- ->thermistor
- -.>resistance drops in hot conditions
- ->resistance goes up in cool conditions
what are Ac supplies?
- ->constantly changing direction
- ->produced by alternating voltages
- ->positive and negative ends alternating
what is the direct current?
- ->Current that is always flowing in the same direction
- ->created by a direct voltage
What is the uk mains supply?
230v
What Is the frequency of the ac mains supply?
50 hertz
What is the national grid?
A giant system of cables and transformers that covers the UK
Why does the National grid use a high potential difference and a low current?
> a high current makes the wires heat up transferring thermal energy to the surrounding
too much energy is lost
What does a step-up transformer do?
> potential difference is increased and current is decreased
>have more turns on the secondary coil
What do step-down transformer do?
> reduces potential difference and increases current
>more primary coils than secondary
