Electricity Flashcards
Current
The amount of electrical charge that is transferred per second
The amount of electrical charge that is transferred per second
Current
What is current measured in?
Amperes (A)
Relationship between current, charge, and time
charge = current x time, or Q = It
Coulomb
Unit for charge, a group of electrons
Unit for charge, a group of electrons
Coulombs
Conductors
Materials that allow electrical current to flow freely
Materials that allow electrical current to flow freely
Insulators
Materials that make it difficult for charges to move
Insulators
Insulators
Materials that make it hard for charges to move
How do charges move in a circuit?
They are given energy in the supply, this is energy is transformed in components in the circuit
Potential difference
The difference in electrical potential between two points
Voltage is the…
Energy given to each coulomb of charge
Electrons are attracted to…
Protons
Electrons flow from…
The negative terminal to the positive terminal
DC current
Where the current will only flow in one direction around a circuit (from negative to positive)
AC current
The voltage changes between positive and negative continually, so the charges periodically change direction
Resistance
A measure of how much opposition there is to the current in a circuit
Measure of the opposition to current in a circuit
Resistance
Resistance in a series circuit
The current moves through all resistors and components, so experiences all resistance
Resistance in a parallel circuit
Each part of the circuit acts a tunnel for current to move through, but there is less resistance because less current moves through each resistor
Ohm’s Law
The relationship between current and voltage, as well as resistance
The relationship between current and voltage, as well as resistance
Ohm’s Law
What does Ohm’s Law show?
Voltage is directly proportionate to current, and V/I = R
What has to remain constant for a component to be considered “ohmic”?
Temperature
How does temperature affect resistance
As temperature increases, so does resistance
Potential divider
A circuit where each each resistor takes a proportion of the supply voltage
What does the proportion of a potential divider rely on?
The size of each resistor and the total resistance in the circuit
Formula for potential dividers
V1/V2 = R1/R2
Capacitor
An electrical component that stores electrical charge, the voltage across it is equal and opposite to the supply voltage when fully charged
Thermistor
A resistance where the resistance increases as the temperature decreases (TURD)
Light dependant resistor (LDR)
A resistor where increasing light levels decreases resistance (LURD)
Light Emmiting Diode (LED)
A diode that only allows current to flow in one direction
On a circuit diagram the point MUST face the negative terminal
Photovoltaic cell
Converts light energy into electrical energy
Motor
Converts electrical energy into kinetic energy
Loudspeaker
Converts electrical energy into sound energy
Relay
An electromechanical switch where applying a small voltage to the iput with switch on/off a larger current or voltage in a seperate circuit
Transistor
An electronic switch that works by applying a voltage between the base and emitter (it makes it conduct through the emitter and collector)
Voltage required to switch on a transistor
0.7V or more
Application of transistors
Used in potential divider circuits to provide voltage to the transistor when the light levels or temperature are high/low enough
Electrical power
The amount of energy transformed per second
How does power relate to current and voltage
IV can be turned into E/Q x Q/t, so E/t (IV = E/t)
Formulae for power
P =… E/t, IV, I^2R, V^2/R
