Unit D - Electricity Flashcards
Electric charges
Charged particles that exert an electric force on each other.
Static charge
Charges in the surface of an object that remain fixed in one location until they are given a path to escape.
Friction
The force resisting the relative motion of two surfaces in contact.
Electron affinity
The tendency of a substance to hold on to electrons. Shown on the triboelectric series
Coulomb (C)
The unit for electric charge named after Charles-Augustin de Coulomb and equals 6.24*10^18
Conductivity
The ability of materials to hold electrons to move freely in them.
Electric insulator
A solid, liquid or gas that resists or blocks the movement of electrons. Eg. wood, glass and plastic.
Conductors
Materials that allow electrons to change positionsz
Électroscope
An instrument that detects static chargeZ
Electrostatics
The study of static electric charges.
Charging by contact
When electrons transfer from the charged object to the neutral object that it touches.
Induction
The movement of electrons within a substance caused by a nearby charged object without direct contact between them. The induced charge dissipates once the charged object is moved away.
Charging by induction
A charged object is brought near a neutral object and then the neutral object is grounded so the previously neutral object now has the opposite charge to the charged object.
Electrical discharge
When electric charges are transferred very quickly.
E.g. lightning
Circuit
A complete path for electrons to flow through.
Current electricity
The continuous flow of electrons in a circuit.
Electrical load
A device that converts energy into another form of energy.
Switch
A device that turns the circuit in or off by closing or opening the circuit.
Battery
A combination of electrochemical cells made up of an electrolyte and two electrodes.
Electrolyte
A liquid or paste that conducts electricity because it contains chemicals that form ions.
Electrodes
Metal strips that react with electrolyte.
Wet cell
An electrochemical cell that has a liquid electrolyte.
Dry cell
An electrochemical cell that uses a paste.
Potential difference/ Voltage (V)
The electric potential energy between two points in a circuit
Voltmeter
Measures potential difference between two locations in a circuit.
Electric current
The measure of the amount of electric charge that passes by a point in an electrical circuit each second.
Direct Current (DC)
When the current only flows in one direction like in a battery.
Alternating current (AC)
Electricity that flows backs and forth at regular intervals called cycle like the current that comes from generates an powers homes.
Ammeter
Measures current in a circuit in amperes (A).
Resistance
The degree to which a substance opposes the flow of electric current through it. Measures in ohms (omega symbol)
Resistor
Any material that can slow current flow.
Factors affecting the resistance of wire
- Material
- Temperature
- Length
- Cross- sectional area
Transistor
A tiny device that acts as a switch or amplifier in a circuit.
Series circuit
An electric circuit in which the components are arranged one after another in series with only one path way along which electrons flow.
Parallel circuit
An electric circuit in which the parts are arranged so that electrons can flow along more than one path. There are junctions where the circuit splits into different paths and Ana interruption on one pathway doesn’t affect the other pathways in the circuit. Resistance is lessened when there are more pathways. Most electrons will follow the pathway of least resistance.
Ohms Law
As long as temperature stays the same V=IR
Short circuit
An accidental low resistance connection between two points in a circuit often causing excess current flow.
Fuse
A safety device that has a metallic conductor with a low melting point compared to the circuits wires. If the current gets too high the metal in he fuse melts and the current flow stops. A blown fuse must be replaced as it can only be used once.
Circuit breaker
Does the same as a fuse however the wire instead heats up and bend triggering a spring mechanism that turns off the flow of electricity. It can be reset once it has cooled.
Generator
Transform energy of motion into an electric current.
Percent efficiency
Energy out / energy in * 100%
