Chapter #18 - Electrical Quantities Flashcards
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Current
The rate at whic electric charge passes a point in a circuit.
What is needed for an electric current to flow?
- A complete circuit
- Something to ‘push’ the current around the circuit.
- e.g. a battery
Battery
2 or more cells connected end-to-end.
Which way does current flow?
Current flows from the posotive terminal of the battery to the negative terminal.
Direct current
An electric current which always flows in the same direction.
How do most switches work?
By bringing 2 pieces of metal together to complete the circuit (though you cannot usually see this happening).
Why are the wires in circuits made of metal?
Because metals are good conductors of electric current.
Why are the metal wires coverd in plastic (in circuits)?
The metals are usually covered in plastic so that if the wires touch, the electric current cannot pass directly from one to another and cause a short circuit. Plastics arfe good insulators.
What is the symbol and unit for current?
Symbol = I
Unit = Amps (A)
What is actually travelling around the circuit?
Electric charge
What does the power supply (the push) do to the charge in comparison to the current?
The power supply or batter proviedes the push needed to make the current flow. Thos push is the same force that causes electric charges to attract/repel eachother.
Charge
Carried around a circuit by the current; negative charge is carried by electrons.
Why are metals good electrical conductors?
Because they contain electrons that can mive about freely. While most electrons in a metal are tightly bound within their atoms, some are free to move about within the the material. These are called conduction electrons.
How do we measure current?
Using an ammeter
How must ammeters be connected to a circuit?
In a series
In series circuits what is the current?
The current is the sam throughout the whole circuit.
Why are polymers not good at conducting electricity?
Because all of the electrons in the material are tightly bound wu«ithin the atoms or molecules, so, theycannot move.
What does a volatge do to a circuit. (turning in the powes supply)
A voltage (provided by battery or pwer supply) can start conduction electrons moving in one dirction throught the metal, and an electric current flows.
What way do electrons travel in a circuit?
Since electrons have a negative electric charge, they are attracted to the posotive terminal of the battery.
Which way does conventional electric current flow?
From positive to negative. But, in a metal it is the negativley charged electrons that move.
What 2 things does an ammeter measure?
- The current in a circuit
- The rate at which electric charge flows past a point in a circuit.
What is the equation for current?
Current = charge/time
I = Q/t
What is the symbol and unit for charge?
Symbol = Q
Unit = Coulombs (C)
