Electricity GCSE Flashcards
cell/battery
Provides the circuit with a voltage
Switch
Turns on/off circuit
Fixed Resistor
Resistor limits flow of CURRENT. Resistance cannot be changed
Variable resistor
A resistor with a slider that can change its resistance
Thermistor
Resistor depends on temperature, as temperature increases, resistance decreases
Light dependent resistor
Resistance depends on light intensity, as light intensity increases, resistance decreases
Diode
Allows current to flow in one direction only
Light-Emitting Diode
Diode which emits light as current passes through it
Ammeter
Used to measure current in circuit
Voltmeter
Used to measure voltage in a circuit
What does a circuit require to work effectively
An energy source of PD
A complete circuit as a loop
Electrical components
How is an ammeter connected to a circuit?
In SERIES
How is a voltmeter connected to a circuit?
In PARALLEL to the component which’s voltage is being measured
What is the direction of flow in a circuit?
From the POSITIVE to NEGATIVE terminal of the power supply
What are some sources of PD?
Cells, batteries, electrical generators
What is PD?
Energy transferred per unit of charge
V = E / Q
What is current?
Rate of flow of electric charge
What is the unit for charge?
Coulomb (c)
What is the equation for Charge?
Q = IT
What is convectional current?
The flow of positive charge from the POSITIVE TO NEGATIVE terminals of a cell
What is special about current in a closed circuit?
Current is the same at every point of a closed series circuit
What do resistors do?
Resist current, the higher the resistor the lower the current.
Good conductors have low resistance, bad conductors have high resistance
What is the unit for resistance?
Ω
1 volt per amp
What does the current through a component depend on?
- Resistance of component
- Potential difference across component
Equation for voltage
V = IR
Required Practical for Resistance
Measuring how resistance changes as length of wire changes
- Length of wire is directly proportional to the resistance
Errors
- Systematic (Crocodile clips could have not started on 0. Ammeter and Voltmeter could be faulty)
- Random (current could have NOT been turned off, so temp of wire increased affecting precision)
Safety considerations -
- High current means high temperature, so wire could be hot
- No liquids close to the experiment
What is Ohms law?
The current through a conductor is DIRECTLY PROPORTIONAL to the potential difference across it. ONLY RELEVENT AT CONSTANT TEMPERATURES
V = IR
Ohmic conductors are conductors that obey this law
What is special about a filament lamp (ohms law)?
- Non Ohmic conductor
- Because resistance of lamp increases as temperature of lamp increases
- Temp increases because of higher current
Why does temp increase as current increases in a filament lamp?
- As current increases, temp increases
- So the fixed atoms of the lamp vibrate more
- Causing an increase in resistance because electrons find it harder to pass through
- Causing the current to increase at a SLOWER RATE
Linear Electrical Components
- Fixed resistors
- Wires
- Heating elements
Non-Linear Electrical Components
- Filament lamps
- Diodes & LEDs
- LDRs
- Thermistors
How can thermistors be used
- Ovens
- Fridges
- Thermometers
- Fire alarms
How can LDRs be used?
- Alarm clocks
- Security lights
Characteristics of a Series Circuit
- Current is same at all points
- Total PD is shared between components
- Total resistance is sum of all resistors
Characteristics of a Parallel Circuit
- Total current through whole circuit is SUM of the currents through the separate branches
- PD across each component is the same
- Total resistance of two resistors is less than the resistance of the smallest individual resistor
What is static electricity?
- Where two electrically insulating materials are rubbed against each other
- And electrons are transferred from one to the other
