Electrical Cells And Circuits Flashcards
What is a cell
It is a source of electrical energy and generates electricity by using chemical reactions
What does an electrical cell consist of
An electrical cell consists of two solid electrodes and electrolytes
What is an electrolyte
Solution that can conduct electricity
What does an electrolyte consist of
Thousands of positive and negative ions
What happens when two electrodes are connected in a circuit
A chemical reaction takes place in the cell which causes the flow of electrical charge (electrons) through an external circuit
What energy conversion takes place in a cell
There is chemical potential energy in the cell —> chemical energy —> electrical energy —> Kinect if energy
What is potential difference
The work done per unit positive charge
What is voltage measured in
Volts (V)
What type of cells are used in our toys, phones and torches etc
Dry cells
What type of battery does a car battery use
A wet cell
What is a battery
When two or more cells are connected in series
What are the two ways a cells can be connected in a battery
Series and in parallel
What happens to the voltage when cells are connected in series
The voltage is added and produces more energy to the charges that move through the circuit
What happens to the voltage when cells are connected in parallel
The voltage is the same as one cell
What are the two ways to make an electric cell yourself
Firstly By means of using a lemon, a coin and a nail. When you take a lemon put a coin on one side and a nail on the other. When you connect conduction wire (coin is the positive electrode and the coin is the positive electrode) and an LED light it will light up.
Secondly by means of a copper sulphate solution, copper plate and zinc sulphate solution and zinc plate. When you take a copper plate and put it into a beaker full of copper sulphate solution and take a zinc plate and put it into a beaker full of zinc sulphate solution then you use a paper towel and soak it in either solutions then put one side in one beaker and the other side in the other. When you connect conduction wire (positive terminal on copper plate, negative terminal on the zinc plate) and an LED light it will light up
What is the positive electrode called
The anode
What is the negative electrode
The cathode
When is a cell flat
When the chemical energy un the cell is depleted and all the chemicals in the cell are used up
What pair of metals makes a cell with the greatest voltage
Copper and magnesium
What happens if the same metal are used to create a cells electrodes
The voltage will result in 0
What is an insulator
Materials that do not allow electrical charges to flow through them
What is an electric current
The rate of flow of an electric charge
What is a conductor
A material which allows charges to flow through it. They are mostly metals
What Is electrical resistance
The resistance offer d by a conductor against the flow of current
What is a good conductor
A conductor with a low resistance and allows a strong current through.
What is a resistor
An electrical component that goes against the flow of current
What does a resistor consist of
Conductive material with a high resistance
Why do we use resistors in circuits
To control the current or for the provisions of useful energy transfer
What are ways resistance is used for electrical appliances
Nichrome is used for heating elements in electrical appliances because it has a very high resistance eg stoves
How does a lightbulb light up
The filament of a lightbulb is made of very thin tungsten wire which produces a bright light when the wire becomes very hot.
What are the factors that influence the resistance of a conductor
Type of material, length of the conductor, thickness of the conductor and temperature of the conductor
How does the type of material Influence the resistance of a conductor
Different conductors have different levels of resistance against electrical current. Eg copper wire conducts a greater current than an equal length of Nichrome wire with the thickness and temperature.
How does the length of a conductor influence the resistance of the conductor
The longer the wire this more resistance and the less the current, the shorter the wire the less the resistance and the more the current
How does the thickness of the conductor influence the resistance
The thinker the wire the less the resistance and the more the current. The thinner the resistance the more the resistance and the less the current
How does the temperature of the conductor influence the resistance of the conductor
Hotter conductors offer more resistance and less current than colder resistors which offer less resistance and more current
What does current consist of
Negatively charged particles that are called electrons
What are the two types of current
Conventional current and electron current
What is conventional current
An electrical current where the charges flow from the positive pole to the negative pile of the cell or battery
What is an electron current
A current where the charges flow from negative to positive
Which current do we use when working with electrical circuits and why
We use conventional current to keep with the internal decision
How is an ammeter connected in the circuit
In series
What is used to measure electrical current
An ammeter
How much resistance does an ammeter have
An ammeter has little to no resistance therefore it measures the current accurately
How do we connect the wires of an ammeter into the circuit
The black (negative contact socket) should lead to the negative pole of the battery. The red (positive contact socket) should lead to positive pole of the cell or battery.
What May damage an ammeter
When it is connected the wrong way around, or connected in such a way that the needle moves to the end of the scale
When charges lose energy in what form do they transfer the energy to the resistor
In the form of heat, light or sound energy
What measures voltage
A voltmeter
How is a voltmeter connected in a circuit
It’s connected in parallel
How much resistance does a voltmeter offer
A great resistance
How must the wires of a voltmeter be connected in a circuit
The same as an ammeter. The black (negative ) contact socket leads to the negative pole of the cell or battery. The red (positive) contact socket leads to the positive pole of the cell or battery
What does resistance control
The current and voltage in the circuit
What is a rheostat
A resistors who’s resistance is adjustable
How does a rheostat work
It has an ordinary resistor with a fixed resistance. Then it has a sliding contact which changes the length of the resistance wire through which current flows and therefore also it’s resistance
When are cells connected in series
One after another an positive to negative
When are cells connected in parallel
Positive pole to positive pole and negative pole to negative pole
How do we calculate the total voltage of cells in series
We add the voltages of the individual cells
How do we calculate the voltage of cells connected in parallel
When cells are connected in parallel the voltage over them will be the same as for only one cell
What is the difference between cells in series and cells in parallel
Cells in series deliver a stronger current because all the cells work at once but it doesn’t last as long as cells connected in parallel because the cells in parallel are used one at a time.
What happens to the current in a series circuit
It is the same throughout the circuit
What happens to the current in a parallel circuit
The current is divided and the sum of the currents going through the resistors is the same as the main current going through the battery
What happens to the voltage in a series circuit
The voltage of the resistors added together should equal the total voltage over the battery or cell
What happens to the voltage in a parallel circuit
The voltage is the same
What happens to resistors connected in series
The resistor with the highest resistance will have the highest voltmeter reading and the resistor with the lowest resistance will have the lowest voltmeter reading. When resistors are added in series the the total current is decreases.
What happens to resistance in parallel circuits
When resistors are added in parallel the total resistance decreases and the total current is increased. Parallel resistors are referred to ad current distributors
What is the difference between a parallel and a series circuit
- In a series circuit the components are connected one after another while In a parallel circuit they are connected in parallel to one another
-if a light break breaks or fuses in a series circuit the rest of the lightbulbs won’t work whereas if a light bulb breaks or fuses in a parallel circuit the rest will still work.
-when lightbulbs are connected in series the fainter the lightbulbs will shine when more are added, whereas when lightbulbs are added in parallel the lightbulbs will stay at the same brightness even if more lightbulbs are added.
What is ohms law
The current through a conductor is directly proportional to the potential difference across the conductor at a constant temperature
What is the relationship between current and voltage
Current is directly proportional to voltage
What is the relationship between voltage and resistance
Voltage is directly proportional to resistance
What is the relationship between current and resistance
Current is inversely proportional to resistance
How is the lighting in our house connected
In parallel
What is the electrical power supply in our houses
220V and 60A
What are safety devices used in a circuit
Fuses, circuit breakers and earth leakage breakers
What is a fuse
A safety device used to protect a circuit against the heating effect of an electric current. It consists of a very thin piece of wire with a low melting point which is connected in series in a circuit so that all the available current May flow through it.
How does a fuse work
When the current gets to strong it heats up the wire and it melts. This breaks the circuit and current stops flowing
What does an electricity distribution board look like
It consists of a big red main switch, a big black Earth leakage circuit breaker and a bunch of smaller circuit breaks
What are circuit breakers
Electric switches (electromagnetic) that are connected to a room or appliance that automatically switches off the flow of current when an overload or short circuit occurs
What is an earth leakage circuit breaker
A safety device that is able to switch off the electricity supply to all circuits when a current of 30mA or more leaks to the ground
How does an earth leakage circuit breaker work
It continuously tests the flow of electrical current through a circuit. When the amount of current that is drawn through the charged wires in a circuit differs from the quantity that returns through the neutral wire the breaker cuts the power.
How is electricity brought to the main switch
From the power station the electricity is brought to the meter box by means of Overhead wiring or underground cables
Where does electricity flow to from the meter box
To the distribution board
What is the main switch
Used to switch electricity supply to the house on and off
Where is electricity generated
In a power station
What is a power station
A system for the generation of electricity
What is the genera method for the generation of electricity at a power station
To rotate a tubune that in turn rotates a generator
How energy that we use in SA comes from coal
Approximately 3 quarters
Where are most fo the power stations in South Africa
In mpumalanga because there is a rich supply of coal there
What are the steps of how a coal driven power station generates electricity
- Coal in a furnace heats water
- Steam is generated from the water
- The steam turns a turbine
- Which in turn turns the generator which converts the kinetic energy to electrical energy
- The energy is changed to correct the voltage in a transformer
- The electricity is distributed by means of pylons and high tension cables into the national network to houses schools, factories etc
What are the disadvantages of a coal power station
Air pollution, which In turn causes acid rain, and contributes to global warming and non renewable resources are being exhausted
