Modules 4.1-4.2 - Electricity - Charge And Current - Energy, Power And Resistance Flashcards
What do electric circuits require in order to work effectively?
An energy source, a source of electromotive force (e.m.f)
A complete circuit
Electrical components
What is the difference between conventional current and electron flow?
Conventional current is the idea that the current in a circuit flows from positive to negative (proposed when electricity was first discovered).
Electron flow explains that charge carriers are electrons that flow from negative to positive.
When is the direction of current flow important?
When one of the components is a diode or an LED
What is Kirchoff’s first law?
Charge is always conserved
The sum of charges going into a circuit junction must be equal to the sum of charges leaving it
This law is true for charge, so must be true for current as current is the rate of flow of charge
What are protons made up of?
Two up quarks
One down quark
What are neutrons made up of?
Two down quarks
One up quark
What are conductors?
Contain a large number of free electrons per unit volume
What are insulators?
Contain very few free electrons per unit volume
What are semiconductors?
Have number of free electrons between those in conductors and insulators
Intermediate conduction properties
Define electromotive force
The maximum possible potential difference across the energy supply when no current is flowing through
Associated with energy sources where chemical energy is transferred to electrical energy
Define potential difference
Describes how much energy per unit charge is transferred at each component
Associated with components that transfer electrical energy to other forms of energy
What is Ohm’s Law?
The current through a conductor is directly proportional to the potential difference across it, provided that temperature remains constant.
Factors that affect electrical resistance
Material of wire
Length of wire - directly proportional to resistance
Cross-sectional area of wire - inversely proportional to resistance
Temperature of wire
Define power
The rate at which energy is transferred from one form to another.
What are diodes?
Only allow current to flow in one direction Switch on instantly Are very robust Are very versatile Operate with low potentials Have a long working life
