Electricity
- Created by: Ebod
- Created on: 26-07-21 18:18
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- Electricity
- Electrical Quanitities
- Resistance
- resistance against flow of electrons
- symbol R, measured in ohms
- R = V / I
- Potential Difference
- force driving flow of electrons
- provided by cell / battery
- aka voltage, V, and is measured in volt (V)
- V = IR
- Current
- symbol I, measured in amp[ere]s, A
- measure of flow of electrons around circuit
- I = Q / t
- I = V / R
- Charge
- total current that flowed over a period of time
- symbol Q, and is measured in coulombs (C)
- Q -= It
- Power
- P = VI
- P = I^2 R
- symbol P, measured in watts, W
- P = E / t
- Resistance
- Electrical Circuits
- Electronic Components
- Filament Lamp
- resistance increases as temperature increases.
- Diode
- current flows in one direction
- high resistance in the reverse direction.
- current flows in one direction
- Light-Emitting Diode (LED)
- Thermistor
- resistance decreases as temperature increases.
- used in circuit of thermostat
- Light-Dependent Resistor (LDR)
- resistance decreases as light intensity increases
- used in circuits like switching lights on when it gets dark
- Ammeter
- connected in series
- measures current
- Voltmeter
- connected in parallel
- measures potential difference
- Ohmic Conductor
- current d.proportional to voltage
- Resistors
- resistance is constant
- Resistors
- current d.proportional to voltage
- Filament Lamp
- Series Circuits
- if one component is disconnect or broken, the whole circuit stops
- V = V1 + V2
- I = I1 = I2
- R = R1 + R2
- More voltage (force) goes to component with higher resistance
- Parallel Circuit
- still works if one component breaks
- I = I1 + I2
- V = V1 = V2
- 1/R = 1/R1 +1/ R2
- total resistance of 2 resistors < resistance of smallest individual resistor
- as V =IR, when new component added in parallel, total resistance decreases
- when new "loop" added, current increases (more place for current to flow), but voltage is constant, so resistance decreases
- Electronic Components
- Static Electricity
- conductors
- electrons can flow; delocalised
- don't get charged
- gains electrons = negative charge
- Insulators
- electrons can't flow
- loses electrons = positive charge
- sparking
- charge builds, if p.d big enough, electrons can jump across gap between objects
- can occur between charged object and earth / earthed object
- balance out charges
- e.g lightning
- cloth and rods
- polythene rod -ve, cloth +ve
- acetate rod +ve, cloth -ve
- result of imbalance of charge
- Electric Fields
- around any electrically charged object
- field strongest closer to charged object
- can be shown with field lines
- arrows from +ve to -ve
- a second charged object placed in field feels a force
- force stronger as distance decreases.
- high p.d = stronger field
- strong field = electrons in air paticles to be removed
- current can flow through air = spark
- normally insulator, but when ionised is conductive
- strong field = electrons in air paticles to be removed
- electrostatic force
- opposite charges attract
- Like charges repel
- force weaker, the further the objects
- non-contact
- conductors
- Electrical Quanitities
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