Module 4 Part 1- Electricity Flashcards
What is Kirchhoff’s first law
At any junction in a circuit,
the total current entering the junction is equal to
the total current exiting the junction
What is Kirchhoff’s second law
In any circuit,
the sum of the emf is equal to
the sum of the pd
around a closed loop
Therefore energy is conserved
How do you calculate the total resistance of a SERIES circuit
R1+R2+R3=RT
How do u calculate the resistance in a PARALLEL circuit
1/R1 + 1/R2 + 1/R3 = 1/RT
What is emf (electro motive force)
EMF is the energy transferred to the charge carries by the power source
What is voltage/how does it differ from emf
Voltage is the energy transferred by the charge carries around the circuit not just the energy from the power source whereas emf is the energy transferred from the power source to the charge carriers.
What is the equation that links current charge and time
I=change in Q/change in t
What is the SI unit for charge and what is the assigned letter
coloumb which is given by the letter Q
What is the elementary charge and what state the number
The elementary charge is the charge that one electron or proton holds and is presented by the letter e
The quantity is:1.6x10^-19
What is the difference between conventional current and electron flow
Conventional current flows from the positive to the negative terminal
Electron flow flows from the negative terminal to the positive
Usually electron flow is what is used
What is the equation for current
Current = change in charge/ change in time
What is charge
Electric charge is a physical property of a particle that can either be positive or negative
What are the two types of charge and how do they interact
Positive and negative
Like charges repel
Opposite charges attract
What is the charge of an electron (and a proton)
1.6 x10^-19
What is an electric current
Electric current is the moving of charge by a charge carrier
What are some types of charge carrier
Some charge carriers are:
Electrons
Protons
Ions
What is the difference between electron flow and conventional current
Electron flow is from negative to positive terminal
Conventional current is from positive to negative terminal
What is number density and what does it mean
Number density of a material is the number of charge carriers available per cubic meter
The higher their number density the better an electric conductor it is
What is mean drift velocity
Mean drift velocity is the average speed that the electrons in the wire move across the terminals
What is the equation linking current, area, number density, charge and mean drift velocity
I=Anev
What are the rules for a circuit diagram
Straight lines
No gaps
What is the difference between a cell and a battery
A battery is multiple cells used together
What is the electron gun
An electron gun is a device that produces a narrow beam of electrons by generating a p.d between a cathode and anode
What is resistance and what is the equation that links voltage, current and resistance
Every component in a circuit has resistance and it is defined as the potential difference across a component over the current in the component.
This is given by when V=IR is re arranged into R=V/I
What is a diode
A diode is an electrical component made from a semiconductor which only allows current through it in one direction
What is an LED
A light emitting diode is a special type of diode which contains a semiconducting material which gives off light when a current passes through
What it is resistivity
Resistivity is the constant given to a specific material which indicates how much resistance it puts up to current
What three factors change the resistance
Resistivity, length and cross sectional area
What is the difference between a conductor, semiconductor and insulator
Conductor-allows flow of electrons
Insulator-does not allow flow of electrons
Semiconductor-somewhere in between
What is a thermistor
A thermistor is an electrical component made of a semiconductor with a negative temperature co-efficient therefore when temperature increases the resistance drops due to a higher number density in the semiconductor
What is an LDR and how does it work
An LDR is an electrical component which drops in resistance as the light intensity increases
it works via a semiconductor in which the free electrons number density increases when the brightness increases
What is internal resistance and how does it differ from batteries
Internal resistance is the resistance inside the battery that the emf has to overcome, a low internal resistance is used when a high current needs to be generated
What is potential divider circuit
A potential divider circuit is a circuit that splits the potential difference over two resistors by using the principle that voltage is proportional to the resistance on each resistor which can be expressed as V1/V2=R1/R2
What is a potentiometer
A potentiometer is a variable resistor with two terminals and one sliding terminal on top to allow a variable V out
