[custom] 4.1 test Flashcards
What is electric current defined as?
State units.
The rate of flow of charge.
It is measured in Amperes.
How can the current in an electrical circuit be measured?
It can be measured using an ammeter, which is placed in series.
Charge is a ____ quantity, which can be either ___ or ___.
Charge is a PHYSICAL quantity, which can either be POSITIVE or NEGATIVE.
Define the coulomb.
1 Coulomb is the flow of charge in a time of 1 second when the current is 1 ampere.
What is e?
Elementary charge.
1.602x10^-19
How can you calculate charge?
Q = Ne Q = It
What are conducting liquids known as?
Electrolytes. They are commonly ionic solutions.
What does it mean if something is an ionic solution?
Provide an example.
They contain positive and negative ions.
Water with dissolved NaCl.
Charge can be carried in ____ ways depending on the ____ the current is passing through.
Charge can be carried in SEVERAL ways depending on the MATERIAL the current is passing through.
What is the current in metals carried by?
Electrons.
Describe metallic structure.
Lattice of positive ions surrounded by free electrons. The ions are fixed in place, but electrons are free to move around.
What is conventional current?
How does this compare to electron flow?
In what way are electrical currents treated?
The rate of flow of charge from the positive to the negative terminal.
All electric currents are treated as being conventional, regardless of the direction the charge carriers are moving in.
In metals, electrons flow from negative to positive, therefore electron flow is in the opposite direction to conventional current.
State Kirchhoff’s first law.
For any point in an electrical circuit, the sum of the currents in to that point is equal to the sum of the currents coming out of that point.
What is Kirchhoff’s first law a consequence of?
Explain what this is.
The conservation of charge.
Charge is a fundamental physical property, which cannot be created or destroyed, so it must be conserved.
Describe mean drift velocity
When electrons move through a metal, they frequently collide with positive metal ions, resulting in random movement.
When a power supply is connected, the free electrons are attracted towards the positive terminal, but they still collide with the positive metal ions.
The mean drift velocity, v, is defined as the average velocity of the electrons as they travel down the wire, colliding with positive metal ions.
