Electronics Flashcards
On a electric diagram what does the battery look like?
Positive is a long thin line and negative is a short fat one
What does a DC (direct current) current do with flow of electricity?
Its fixed and only flows in one direction
What type of electricity is used in homes and buildings normally?
AC (Alternating current) and in the UK its 50 hertz, and other parts of the world its 60 hertz
What does the effect of an electrical current depend on?
Its magnitude
What is the measurement of electrical current?
Its standardised using the unit of Amperes
What types of switches are there?
Trembler switch, pull switch, reed switch, tilt switches
What are the characteristics of conductors?
Usually metals, one or two weakly bound valence electrons per atom, net movement of electrons is seen as a current, valance electrons use in chemical bond in tarnished or oxidised metal
What are insulators normally made up of?
Plastics, rubber, ionic crystals, glass,
What are the characteristics of semiconductors?
They are between conductors and insulators, number of free electrons tuned by addition of chemical impurities
what is charge?
Charge is the quantity of electricity and measured in C (coulombs)
What is Q=It
Q is magnitude of a charge, I is current and T is time
What is Ampere-hour?
The ampere hour is the quantity of electrical charge that a battery can deliver, for example a 60Ah can deliver 60 amps for 1 hour or 30 for 2 etc
What is W=QV
Electrical work = Magnitude of charge x Volts
Does Voltage drop using different materials due to work done being higher?
Yes
What is power?
the rate of working, or the number of joules work done every second
P =W/t = QV/t
I=Q/t
P=IV
What is resistance?
Resistance is where material prevents some or all electricity flowing through it. Every material has some resistance, resistors used to control amount of resistance and therefore control V and I with a circuit.
What happens in most simple circuits?
In most simple circuits electrical current through a load is proportional to the voltage across it. V=IxR R is known as the electrical resistance measured in Ohms
What is Ohms law?
Power in a circuit - P=IV
Ohms law V=IR
Hence P=I^2R
What happens to resistance at extreme low temperatures?
At extreme low temperatures variation of resistance is no longer linear and at very low temperatures some materials loose all resistance, these are called superconductors
What are the average current and potential difference in AC circuits?
They are both zero but work is still done.
What does having three phases allow?
It allows for high power density to equal out the usage.
When the usage isnt great what type of phases is used?
Single phase
What is a fuse?
A fine wire designed to burn out at a specific current, which acts like a switch.
What is a RCD?
A residual current device provides the user with added protection against electrocution or fire. They detect imbalance in current between live and neutral.
What are diodes?
Diodes act as a one way valve for electricity converting AC to DC.
What is the EMF?
Electromotive force is the voltage generated in a power supply. Potential difference received by a load is always less than the EMF due to voltage lost in cables
What are the characteristics of voltage?
It is generated from electromotive force like a battery and used in potential difference like a kettle.
What are some types of generators?
Primary cells (such as single use battery), Secondary cells( Car batteries)
What must current going into a junction equal?
It must equal the total current coming out of the junction
What must the sums of potential differences around a circuit equal?
it must equal the sum of the emfs. Total voltage used = total voltage generated
What happens with equal resistors to the voltage?
There will be equal voltage drops
What makes up the sum of the resistors?
The total of all the individual resistors
What is another name for a variable resistor?
Potentiometers or rheostats
Have you heard of Joe?
Joe mama
He lives in Sekondis
Sekon-dis nuts ayyyyy
What does a larger cross section do to the resistance?
It lowers the resistance
What is resistance proportional to in copper wires?
Resistance is inversely proportional to area
What is wire resistance proportional to?
Wire resistance is proportional to length, which is then inversely proportional to its cross sectional area
What is resistance?
How much an object opposes flow of electrons, and depends on the objects size and what it is made of?
What is resistivity?
Intrinsic property of a material, and doesnt change with length or cross sectional shape
