P6: Static, Current Electricity and Circuits Flashcards
Tool to remember circuit calculations
- Draw 5 triangles in the order shown in the diagram
- place one unit symbol at each vertex of each triangle and between the vertices of adjacent triangles starting from the left and in an up-down pattern.
- The symbols to be selected are taken from the nemonic:
Can Julie Visit W***_atson _***A***_nd _***C***_arry _***S***_ome _***Jellybeans With A***_ssorted _***Raisins?
Each triangle represents a triangle formula
true or false: Neutral bodies have the same number of negative and positive charges
- true
true or false: in metals both electrons and protons can be mobile
false: the positive charges remain fixed
true or false: electron flow in the same direction of conventional current flow
false: the flow is opposite
true or false: all matter contains positive and negative charges
true
true or false: the positive and negative charges in a liquid can be mobile
true
define electrostatic induction
process by which electrical properties are transferred from one body to another without physical contact
in terms of electrostatics, what happens if a glass rod is rubbed with a piece of cloth
electrons transfer from the glass rod to the cloth resulting in a positively charged glass rod and negatively charged piece of cloth
in terms of electrostatics, what happens if a polythene(plastic) rod is rubbed with a piece of cloth
electrons transfer from the cloth to the polyethene rod resulting in a positively charged cloth and negatively charged of rod
true or false: an charged body can attract an uncharged one
true.
what subatomic particle is used to explain electrostatics
the electron
a charged polythene rod is brought near a small piece of uncharged paper and the paper sticks to the rod. Explain what may have happened
the polythene rode is negatively charged and the electrons on its surface repel the electrons on the surface of the paper, leaving a net positive charge which is now attracted to the negative charge on the rod
what are some useful applications of static charge
- lightening conductors to protect buidings
- use in electrostatic dust precipitators to reduce pollution of the environment from dust and carbon particles contained in smoke
- electrospraying of objects such a motorvehicles
- photocopiers
how is electric current carried in metals and graphite?
by electrons
how is electric current carried in a molten metallic compound?
ions
Electrical field from negative charge
what idealized model is used to study electric fields?
the positive test particle
Electrical field form positive charge
- what charge does this particle possess?
- where is the electric field strongest?
- its positively charged because the electric field goes outward from the particle
- the electric field is strongest nearest to the particle because the field lines are closest together near the particle
two charged plates A and B are placed near each other.
- what is the charge on plate A
- what is the charge on plate B
- plate A is positive
- plate B is negative
- what charge does this particle possess?
- where is the electric field strongest?
- its negatively charged because the electric field goes toward the particle
- the electric field is strongest nearest to the particle because the field lines are closest together near the particle
two particles A and B are in an electric field
- what is the charge of paricle A
- What is the charge of particle B
- where is the field strongest between the particles?
- Where is the weakest field between the two particles?
- charge on particle A is negative
- charge on particle B is positive
- electric field between them is strongest at C.
- the weakest electric field between them is at D
two charged particles A and B arein an electric field
- what is the charge of paricle A
- What is the charge of particle B
- Describe the electric field at C
- charge on particle A is negative
- charge on particle B is negative
- no electric field at C as the resultant electric force is 0
two charged particles A and B are in an electric field
- what is the charge of paricle A
- What is the charge of particle B
- Describe the electric field at C
- charge on particle A is positive
- charge on particle B is positive
- no electric field at C as the resultant electric force is 0
how is electricity charge carried in ionic solutions ie solutions of salts
ions
what is electric current?
electric current is the rate of flow of electric charge
what is the equation to calculate elecric current
I = Q/t
Q is electric charge
t is time the the charge flows for.
what is the unit of current?
Amperes(A)
what is the unit of electric charge?
Coulomb(C)
What is the definition of the Coulomb
The unit of electric charge
what is the equation for calculating the amount of electric charge?
Q = I x t
- Q is charge*
- I is electric current*
- t is time*
what is the Faraday constant?
The charge on 1 mole of electrons which is equal to 96500 C/mol
what is an electric field?
an electric field is the region in which a body experiences a force due to its charge
what is the difference between electron flow and conventional current
electron flow is movement of negative charge conventional current is the direction in which a positive charge would move if it were free to do so. It is the direction of the electric field
what is the direction of an electric field?
The direction of the field is taken to be the direction of the force it would exert on a positive test particle. The electric field direction about a positive test particle is always directed away from the positive source.
what is alternating current?
Alternating current describes the flow of charge that changes direction periodically.
what is direct current?
the flow of charge in only one direction.
what is frequency of the a/c source?
number of oscillations or cycles per second. unit is Hz(Herts)
in electricity calculations it is determined by :
f = 1/T
what is Periofd (T)
time taken to complete one oscillation
T = 1/f
sources of A/C current
electric generators
sources of direct current
cells and batteries
what is rectification?
the process of converting a/c current to d/c current.
types of rectification
- half wave and
- full wave rectification
what electrical component carries out rectification and how?
a diode carries out rectification and does it by only allowing the electric current to flow in one direction
what is a capacitor
a simple device that stores electric charge for a short period of time
what is a semiconductor?
material with conductivity between that of a conductor and an insulator
main substance used as a semiconductor
silicon
important function of a semi conductor such as silicon
used to make many components of electric circuits
What does potential difference(pd) across a conductor mean?
the potential difference between two points in a circuit is the energy used (or work done) in transferring a unit charge between those 2 points.
what is electromotive force(emf) of a cell?
The emf of a cell is the energy used(or work done) in transferring a unit charge around a complete circuit, including the cell itself
what is the unit of pd and emf
The volt, V
when is emf used?
when referring to the pd in a cell or battery
what is the equation for emf and pd
V=E/Q
- V is voltage
- E is electrical potential energy
- Q is electrical charge
what is a positive test particle?
a positive test particle is an arbitary model of a positively charged object that can be influenced by an electric field but its presence does not affect the electric field.
how do we define 1 Volt?
1 volt is the potential difference existing between 2 points when and energy of 1J is required to tranfer 1 Coulomb of charge bwteen those 2 points
common electrical quantities used in electrical circuit calculations
6 main electrical quantities
- power
- energy
- voltage
- current
- charge
- time
Joules Law
what is Ohms law
the current through a conductor is directly proportional to the potential difference across it, as long as its physical properties and conditions remain constant.
The equation is V= IR
Graph demonstrating Ohms Law
what is an ohmic conductor
a conductor that obeys Ohm’s Law (such a simple metal)
- This the graph what possible device?
- Is it an ohmic conductor?
- A diode
- No, because the grpah is not a straight line
- This the graph what possible device?
- Is it an ohmic conductor?
- a filament lamp
- No, because the IV graph is not a straight line
in terms of potential difference, in which direction does electric current flow?
from a region of higher pd to a region of lower pd
relationship between the emf of a cell and pd between two points in a circuit connected by that cell
the sum of the pd of the different components of the circuit add up to the emf of the power supply. The greater the emf of a cell, the greater the pd between any 2 points in the circuit
what is understood by 1 watt (1W)
1 joule per second (1Js-1)
what is an electrical circuit?
the path throught which an electrical current flows
diagram representation of a simple circuit
A simple electrical circuit will contain these 3 main parts
- power source(source of emf) eg battery or cell
- electrical components eg resistors or lamp
- leads(wires) to connect the different components
how many categories of electric circuits are there
2- series and parallel circuits
what is the source of the emf in a circuit?
cell, battery or power supply
what is the main between a series and a parallel circuit
a series circuit has no branches while a parallel circuit is branched
characteristics of a parallel circuit
- has junctions and branches so the current has 2 or more paths to flow
- the current entering any junction is the same as the current leaving the junction, so the total current is the sum of all the currents through each component
- the voltage across each component is the same.
- if a component is disconnected or broken at any point in the circuit, the other components in the other branches will keep working
- as more components(resistance) are added to the circuit the total resistance decreases and the total current increases and so more current flows through each component, eg bulbs added to a parallel circuit will keep the same brightness.
- to find the total resistance of a parallel circuit is calculated using the following formula:
1/Rt = 1/R1 + 1/R2 + 1/R3 + … “
characteristics of a series circuit
- no junctions i.e. no branches
- current (electrons) passes through all the components one after the other because there is only one path
- all the components carry the same current
- if a component is disconnected or broken at any point then no current will flow and all the components will stop working.
- the voltage across each component is different
- as the number of components(resisitance) increases, the total current in the circuit decreases, eg the more bulbs added means each bulb will have less current and will be less bright.
- the total resistance of a series circuit is equal to the sum of the individual resistances
A (1)_______________ is connected in (2)__________ with a (3)__________ in a circuit in order to measure the (4)___________ across it, and has (5)____________ resistance. An (6)___________ is connected in (7)_________ with a (8)_____________ with order to measure the (9)_____________ throught it and must have (10)__________ resisitance.
- voltmeter
- parallel
- component
- potential difference
- infinite
- ammeter
- series
- component
- current
- zero
example of a parallel circuit
series circuit
is this a parallel or series circuit?
series circuit
is this a parallel or series circuit
parallel circuit
is this a series or parallel circuit?
parallel
is this a series or parallel circuit?
series
equations to know when doing electric circuit calculations
Four main parameters in each quadrant of the circle.
- power - unit is watts(W)
- Voltage - unit is volt (V)
- Resistance - unit is ohms(Ω)
- Current - unit is Amps(A)
what is the rule for current in series circuit?
the current is the same at all points in the circuit
what is the rule for the current in a parallel circuit?
the sum of the current in the branches is equal to the total current outside the branch
what is the rule for voltage in series circuit?
the sum of the different potential differences across the individual resistors is equal to the total potential difference across the whole group
what is the rule for voltage in parallel circuits?
the potential difference across each resistor or component is the same and is equal to the potential difference across the group
If two resistors are connected in parallel, their combined resistance is (1)_________ than the resistance of (2)________ of the resistors
- less
- each
what are the 3 equations used to calculate power in a complete circuit
These 3 equations are dreived from the genreal equation for power: Power = energy/time (P = E/t)
what are the 3 equations used to calculate energy dissipated in a circuit?
These 3 equations are derived from the general equation for energy: Energy = power x time (E = Pt)
A (1)_________ is a single unit that converts chemical energy into (2)__________energy, and a (3)__________ is a collection of cells.
- cell
- electrical
- battery
A (1)____________ converts chemical energy to (2)_________ by a non-reversible chemical reaction. A (3)_____________ converts (4)_________ to (5)_________ by a reversible chemical reaction and can be (6)_________ by passing current throught it the (7)___________ direction of the current that discharged it.
- primary cell
- electrical energy
- secondary cell
- chemical energy
- electrical energy
- recharged
- opposite
If each cell in a battery is connected in series, the emf of the battery is equal to:
the sum of the emf of each cell
eg. a battery made by connecting 5 cells each with an emf of 2V will have a total emf of 10V
15 cells each having an emf of 1.5V are connected in series to make a battery. what is the total emf of the battery?
total emf is 15 x 1.5V = 22.5 V
If each cell in a battery is connected in parallel, and the cells have similar emf, the emf of the battery is equal to:
the emf of the battery is equal to the emf of one of its cells.
eg. if 3 similar cells each of emf 2.1V are connected in parallel to make a battery, the battery will have an emf of 2.1V
a battery is made by connecting 50 similar cells, each of 1.5V, in parrallel. what is the emf of the battery?
1.5V
what is the advantage of batteries made of cells in parallel?
these batteries will last longer because each has to produce only a portion of the total current output of the battery
what happens to the current that enters a parallel circuit?
- it is shared amongst the components of the parallel circuit therefore each component uses a fraction of that current.
Note: the current entering the parallel circuit is equal to the total current leaving the parallel circuit.
what happens to the current that enters a series circuit?
- the same current passes through each component in series
Note: the current entering the series circuit is equal to the current leaving the series circuit
what happens to the pd when a current enters a parallel circuit?
- it is the same across each component
what happens to the pd(voltage) when a current enters a series circuit?
it is shared between each component.
Give an examle of a primary cell
- The zinc carbon dry cell
give an example of a secondary cell
the lead acid accumulator - commonly known as the car battery
How does the zinc-carbon dry battery procude its emf?
- the emf is produced by an irreversible chemical reaction that produces electricity.
- the cathode: graphite rod
- the anode: zinc
- the electrolyte: ammonium chloride paste
- reaction occurs between zinc, carbon and the ammonium chloride paste, producing an electromotive force (emf) which is 1.5V initially.
how does the lead acid battery poduce its emf?
a reversible chemical reaction in the battery produces an electric current
- anode - lead oxide plate
- cathode - lead plate
- electrolyte - dilute sulphuric acid
- emf of 2V produced by each cell
- 6 cells place in series to produce a total emf of 12V
This is an example of a (a)___________ battery. Its emf is produced by a (b)__________ reaction. based on its electrodes it is called a (c)________ battery
Its labelled parts are:
(a) primary, (b) non-reersible (c) zinc-carbon
- metal cap
- positive carbon electrode
- negative zinc electrode
- paste of ammonium chloride solution
- magnesium(IV) dioxide
- Negative contact
Advantages of zinc-carbon batteries over lead-acid batteries
- small and light
- contents do not spill
- less costly
- batteries of various emf(voltages) can be made packing the cell in series or parallel.
Advantages of lead acid cells over zinc-carbon cells
- much larger currents can be produced
- can be recharged
- has much lower internal resistance
what are the differences between zinc-carbon cells and lead-acid cells?
what are the advantages of having parallel circuits in the home
- appliances can be switched off without affecting the others
- appliances can be designed to operate on a single voltage as the pd across each component in parallel is the same
what is a fuse
- a thin, short piece of wire which is placed in series with a circuit to protect the components for large currents.
- each fuse has an amp rating and if the current goes above it the wire melts, therby breaking the circuit and stopping the flow of electric current.
what is a circuit breaker?
works similarly to fuses except they use a magnetic switch. If the current is too high the magnetic strip will ‘open’ the circuit and cut of current to the components thus protecting them from electrical damage and reducing the risk of fires.
what is the earth wire?
The earth wire wire with low resistance wire conductor that connects the metal casing of some appliances to the earth, reducing the risk of a fatal electric shock. If a live wire breaks off in the appliance and touches the metal casing the current will go to earth and not though the person using the appliance
Draw a simple circuit diagram for recharging a secondary battery
Note that the negative electrode of the cell is conected the negative electrode of the power supply, forcing the current to go in the opposite direction to its normal flow, ie back into the cell.
What is a logic gate?
A logic gate is an electronic component which processes one or more input states(0 or 1) to produce a single output(0 or 1)
What is a binary code
A code that has only two numbers: 0 and 1
What are the 3 basic logic gates and their symbols?
Do the digits 0 and 1 represent in logic gates?
- The digit 0 is called logic 0 and has low voltage.
- The digit 1 is called logic 1 and has high voltage
what is the symbol for the NOT logic gate and what does it mean?
it produces an output which is NOT the same as the input.
So when there is a logic unput of 0 the logic output is 1 and vice versa
what is the OR logic gate and how does it work?
This logic gate produces a logic 1 output if one OR the other of its inputs is logic 1
what is the symbol for the AND logic gate and what is its function?
This logic gate produces a a logic 1 if its first input AND second input are both logic 1
symbol for the NOR logic gate how it works
any 1s produces a 0, otherwise the output is 1
symbol for the NAND logic gate and how it works
two 1s produce a zero, otherwise the output is 1
When working out logic gates in electronics the 0 or 1 input is based on a simple logic which is?
whether or not the condition is true or false
eg if the condition is true the the input is 1
if the condition id false then the input is 0
in order to know what the output of a logic gate or combination of logic gates is we need to……….
contruct a truth table based on the logic gates being used to produce the output
truth table for the NOT logic gate
truth table for the AND logic gate
truth table for the OR logic gate
truth table for the NAND logic gate
truth table for the NOR logic gate
truth tables for the 3 basic logic gates
How to construct a truth table for combination of logic gates
- Each input gets its own column and the output also gets it own column
- the number of rows the tablel has depends on the number uf inputs. we use the forlmula 2x, where x is the number of inputs.
1 input = 21 = 1 row
2 inputs = 22= 4 rows
3 inputs = 23= 8 rows
- each column has the same amount of 0s and 1s
Advantages of electronic and technological advancement
- businesses get a competetive edge when they use more advanced technologies
- improved communications
- smart devices to improve productivity
- greater access to information eg google
Advantages of electronic and technological advancement
- vast amount of incorrect information online
- addiction to social networks resulting in decreased productivity
- decreased social skills becuase of virtual communications eg social media
- exposure to inappropriate content such pornography and violence
- loss of jobs due to the use of more efficient machinery
- manipulation and theft of information and digital resources by unscrupulous hackers
