Electrical Circuits Flashcards
Charge
A convention that describes whether a particle is ‘positive’ or ‘negative’.
How is the electric current carried?
The electric current can be carried by discrete electric charge carriers, such as protons, electron, or ions.
Recall the law of conservation of electric charge
The net amount of charge produced in any transfer process is always zero. The charge lost by one object is the charge gained by another.
Kirchoff’s Current Law
Electric current is conserved at all points in an electric circuit. The sum of current flowing into a node is equal to the sum of the current flowing out of a node so that charge is conserved.
Electric current
The rate of motion of electrons from one part of a conductor to another.
I=Q/t
Where Q is the total amount of charge passing a given point at any second, and t is time.
Electric potential difference
The difference in electric potentials between two points in an electric field.
Power
The rate at which work is done or energy is transferred or transformed.
P = W/t = Js^-1
P=VI
P=I^2R
W=VIt
Explain Kirchoff’s Voltage Law
Kirchoff’s Voltage Law states that the sum of the potential differences of all the resistors around a closed loop is zero. The energy input into a circuit equals the sum of energy outputs from the loads in a circuit.
Recall what electrical potential difference measures?
Electrical Potential difference measures the energy available to moving charges in a current, relative between two different points.
Explain why electric charge separation produces an electrical potential difference
Potential energy is the energy available due to the position of an object in a field. If an electric charge has more potential energy than another, it means that it is more relatively energised because there is a greater magnitude between it and another, oppositely charged particle.
Define Resistance
Resistance is the opposition to the electric current in a circuit measured by the ratio of the voltage applied to the electric current that flows through it.
Compare and Contrast Ohmic and Non-Ohmic Resistors.
Ohmic Devices
- follow Ohms law
- a linear relationship between voltage and current
- resistance is constant
Non-Ohmic
- Do not follow Ohms law
- Inverse Square relationship between Voltage and Current
- Resistance increases as voltage increases, because as volage increases temperature increases, and as the temperature increases resistance increases
Define Power Dissipation
The measure at which energy is lost from an electrical system.
What are the characteristics of resistors in series and parallel
Resistors in Series
- The sum of the resistances is the total resistance
- The current is the same through all resistors
- The voltage is divided amongst the resistors
Resistors in Parallel
- The sum of the resistors = 1/Rt =1/R1 + 1/R2 + 1/R3 + … 1/Rn
- The current is divided amongst the branches
- The voltage is the same amongst the branches
