Zusammenfassung der Ressource
Circuits
- Circuit Devices
- Current flows in one direction = Diode
- Light-Emitting Diode (LED)
- emits light when current flows in forward direction
- uses smaller current - indicate presence of current - used to show something's switched on e.g. TV
- LDR
- dependent on light intensity
- in bright light, resistance falls - high current e.g. automatic night lights
- Thermistor
- temperature dependent
- in hotness, resistance drops - high current e.g. temp. detectors
- Build up of Static is caused by Friction
- when certain insulating materials rub against
each other, negatively electrons get scraped off
- leaves positive charge on one/negative on other
- which way electrons move - depends on two materials
- electrically charged objects attract small objects around
- Only Electrons Move
- Current & Potential Difference
- Current = flow of charge (Amps)
- only flows if there's voltage
- Potential difference = driving force that pushes current (Volts)
- Resistance = anything that slows down flow (ohms)
- the greater the resistance, the small the current
- Current = Charge ÷ Time
I = Q ÷ T
- Amps, coulombs, secs
- P.D = work done per coulomb of charge between two points in circuit
- amount of energy per unit of charge
- P.D = Work done ÷ Charge
V = W ÷ Q
- Basics
- Symbols
- Fuse
- LED
- LDR
- Resistor
- Variable
Resistor
- Ammeter
- Voltmeter
- Diode
- Thermistor
- Ammeter/Variable Resistor = Series
- Voltmeter = Parallel
- Series Circuits
- P.D = Shared
- add up to source voltage
- Current = Same Everywhere
- Resistance = adds up
- bigger resistance of component = bigger share of P.D
- Parallel Circuits
- P.D = Same across All components
- Current = Shared
- adds up
- Resistance & V = I x R
- Resistance increases with temperature
- some electric energy = transferred to heat energy
- ions in conductor vibrate more = more difficult for electrons to get through resistor - current can't flow & resistance increases
- graph for bulb levels off
- Potential Difference = Current x Resistance
V = I x R
- diode = flow only one
direction/high resistance
in opposite direction
- resistance = directly
proportional to P.D
(at constant temp.)
- as temp. of lamp/bulb
increases, resistance
increases