Module 4 Flashcards
What is current?
The rate of flow of charge.
What is current measured in?
Amperes
What is an ampere?
One coulomb of charge passing a given point per second.
What is a coulomb?
The electrical charge flowing past a point in one second when there is an electrical current of one ampere.
What is the elementary charge?
The charge on one proton. It is equal to 1.6x10^-19 C
How do you calculate the net charge on an object?
Q=+-ne, where Q is the charge in coulombs, n is the number of electrons added or removed, and e is the elementary charge.
What can result in a larger current in a metal wire?
- a greater number of electrons moving past a given point each second (a wire with a greater CSA)
- the same number of electrons moving faster through the metal.
What is the direction of conventional current?
From the positive terminal to the negative terminal.
What are electrolytes?
Liquids that can carry an electrical current.
What ions are attracted towards the cathode?
Cations (positive ions).
What ions are attracted towards the anode?
Anions (negative ions).
How do you place an ammeter in a circuit?
In series at the point where you want to measure the current.
What is the conservation of charge?
Electrical charge can neither be created nor destroyed. The total amount of electrical charge in the universe is constant.
What is Kirchhoff’s first law?
For any point in an electrical circuit, the sum of currents into that point is equal to the sum of currents out of that point.
What is Kirchhoff’s first law based on?
Conservation of charge.
What is number density?
The number of free electrons per cubic metre of material. The higher the number density, the better the electrical conductor.
How fast do charge carriers move?
Most move slowly. Free electrons repeatedly collide with positive metal ions as they drift through the wire towards the positive terminal. The reason that lights turn on so quickly is that all the free electrons in the wire start moving almost at once.
How should you draw circuit diagrams?
- Only use correct circuit symbols
- Do not leave any gaps in between the wires
- When possible use straight lines drawn with a pencil and ruler
What is a battery?
Two or more cells connected end-to-end, or in parallel.
How do you tell which end of a cell is the positive terminal?
The longer terminal on a circuit diagram.
What is the circuit symbol for a diode?
A triangle with a vertical line at the point. The wire can be seen through the triangle.
What is the circuit symbol for a resistor/variable resistor?
A rectangle which does not have the wire running through it. A variable resistor has an arrow pointing up and to the right through the rectangle.
What is the circuit symbol for a fuse?
A rectangle which has the wire running through it.
What is the circuit symbol for a thermistor?
A resistor with a “hockey stick” through it.