5. EFFECTS OF ELECTRIC CURRENT

5.1. Heat.
The energy that an electric current produces as heat is called the Joule Effect.
It is expressed by the following formula:
                                                E = I^2 x R x t

5.2. Light.
Incandescent bulbs.
When an electric current passes through the metallic filament of a lightbulbs, it produces light. This phenomenon is called incandescence.

Fluorescent tubes.
Inside a fluorescent tube, there is a metallic filament, normally of tungsten. There is also an inert gas, such as argon, and a small amount of mercury.

Light-emitting diodes (LED)
A light-emitting diode (LED) has layers of semiconductor materials.

5.3. Electromagnetic effects.
In this experiment, the electric circuit has created a magnetic field. This effect can be used to produce movement.

5.4. Sound.
We can transform electric current into sound by using electromechanical devices, such as bells and buzzers. Some of these devices are based on the piezoelectric effect.

4. TYPES OF CURRENT

4.1. Direct current.
Between the terminals of a battery, there is a continuous, stable flow of energy. If we use a voltmeter to measure the current in a car battery, the result will always be 12 volts. This is called direct current.

4.2. Alternating current.
If we measured the voltage of an electrical socket, the results could be represented in a graph like the one below:

• The current begins at 0 V and increases to 325 V.
• The current decreases from 325 V to 0 V.
• The current becomes negative and decreases to -325 V.
• The current increases to 0 V.

The variation of any electrical parameter over a period of time is an electric signal.
The tension or voltage of domestic electricity is an alternating signal because it alternates between positive and negative values. Its waveform is also sinusoidal, with a smooth, regular shape.

4.3. The efficiency of alternating current.
The average power of alternating current is equal to the direct current that is needed to produce the same effect. In the case of an alternating sinusoidal current, the average power would be as follows:
                                                            Vef = Vmax/√2
4.4. Transformers.
Transformers consist of two windings made of copper wire. If we apply an alternating current to one of them, it will produce a certain voltage in the other. The value will depend on the number of times that the copper wire has been wrapped around each winding, represented as n1 and n2:
                                                           V1/V2 = n1/n2

3. TYPES OF CIRCUITS

3.1. Series circuit.

Two or more elements form a series circuit when the output of one element provides the input for the next element.
To calculate the total resistance of a circuit, we add the resistance values of each load:
                                                      R = R1 + R2 + R3 +...
One example of this type of connection would be a series of generators.
In other words:                             V = V1 + V2 + V3 +...
 

3.2. Parallel circuit.
If identical batteries are connected in parallel, the voltage of the circuit will not increase.
The equivalent resistance of this type of circuit would be:
                                                    1/R = 1/R1 + 1/R2 + 1/R3 +...
 

3.3. Combination circuit.
A combination circuit has some elements connected in series and other elements connected in parallel.

2. ELECTRICAL QUANTITIES

2.1. Voltage or potential difference.
The amount of energy that a generator can transfer to electrons depends on its voltage (V) or electric tension. This is measured in volts (V).
This device has two wires that must be connected in parallel to the element that we are checking.

2.2. Measuring electric current.
Electric current is the charge or number of electrons that flo through the cross-section of a conductor every second.
                                                                  I= Q/t 
Electric current is measured in amperes or amps (A).

2.3. Electric resistance: Ohm's Law.
 The resistance (R) of a material is equal to the voltage divided by the intensity of the electric current which travels through the material. This ratio, which is called Ohm's Law, can be expressed as follows:
                                                                              R= V/I
Ohm's Law has two forms:
 V = R x I    and   I = V/R

2.4. Electric energy and power.

Electrical energy.
If an electric current flows at a particular tension for a certain amount of time, we can calculate the energy that is consumed:   E = Vx I x t
Is measured in joules (J).

Electrical power.
The electrical power of a load is the amount of energy that it can transform over a certain amount of time. Electric power is measured in watts (W) or kilowatts (kW).

If an electrical current flows at a particular tension, we can calculate the power (P) that is consumed:
                                                                        P = V x I
We simply multiply the power in kiloatts by the amount of time in hours.
                                                                        E = P x t

7. ELECTRIC CIRCUITS AND ELECTRONICS

1. AN ELECTRIC CIRCUIT.

An electric circuit is a pathway for the flow of electrons.
Electric current is a continuous flow of electrons through a circuit.

1.1. Parts of an electric circuit.
Electric circuits consist of various parts:

• Generators provide the energy that electrons need in order to move.

 

• Loads are devices that transform electric energy into other types of energy that we can use.

   Light bulbs
  Motors

Resistors
 Bells

• Switching devices are used to direct and interrupt the flow of electric current.

  Switches
Push buttons
3-Way switches


1.2. Diagrams and symbols.
Generators: electrochemical cell and battery.
Loads: Light bulb or lamp, resistor, motor, bell, relay.
Switching devices: switch, push button, 3-way switch.
Safety elements: fuse.
Measuring instruments: ammeter, voltmeter.
Other parts: connection and bridge.

8. HOW CAN WE SAVE ENERGY?

8. HOW CAN WE SAVE ENERGY?

There are two important ways we can save energy: by increasing the energy efficiency of the devices that we use and by recycling as much as possible.

8.1. Energy efficiency.

An energy-efficient device requires less energy to perform the same work.

• Lighting: We can reduce the amount of electric light that we use by taking advantage of natural lighting.
• Domestic appliances: New appliances have energy efficiency labels to indicate how much energy they consume.
• Air conditioning and heating: We use a lot of energy to keep our homes at a comfortable temperature, but there are ways we can be more efficient.
• Transport: The best way to consume less energy is to use public transport or to travel with other people when going long distances.

8.2.. Recycling.

Our consumption of manufactured products generates waste and uses energy. We can reduce these negative effects by recycling as much as possible.

8.3. Positive impact.

Energy efficiency has a beneficial effect on the environment.
There are various projects to develop clean energy, such as nuclear fusion, which is the source of our Sun's energy.

7. ENVIRONMENTAL IMPACT.

7. ENVIRONMENTAL IMPACT.

7.1. Environmental impact assessment.

Any proposed new technological project should include an environmental impact assessment. There should also be an assessment of the economic and social repercussions of the project before any important decisions are made.

Wind: it is non-polluting, but it has visual and acoustic impacts, renewable, it is clean and it helps to replace our dependency on fossil fuels and output is low, discontinuous and random.
Hydroelectric: it has a major impact because it changes the flow of rivers and floods large areas, reneable, output is high and efficient and it a dam breaks, the could be a disaster.
Solar: it is non-polluting, but large power stations take up a lot of land, renewable, it is clean and it helps to replace our dependency on fossil fuels and installations are expensive.
Marine: the construction of marine stations affects the local environment, renewable, it is clean and it helps to replace our dependency on fossil fuels and installations are expensive.
Biomass: the technology is beneficial when it is used properly, renewable, it helps to replace our dependency on fossil fuels and it requires an excessive use of natural resources.
Fossil fuels: air pollution contributes to climate changes, non-renewable, output is high and efficient and air pollution causes respiratory illnesses.
Nuclear: radiation is very dangerous if there are accidents, non-renewable, output is high and effcient and it produces radioactive waste.

7.2. Effects on the environment.

 Extracting natural resources.
Fossil fuels and radioactive elements, such as uranium, must be extracted from underground deposits. Large areas of forest have been destroyed to provide wood for fuel.
Transporting fuel.
Most oil is transported over land through pipelines and by sea in large ships called oil tankers. Natural gas is transported over land through gas pipelines or by sea in tankers as liquid natural gas. These tankers are called LNG carriers.
Generating electricity.
Hydroelectric power stations require large amounts f water hich must be stored behind dams in reservoirs.
Waste treatment.
Some steps can be taken to reduce waste and its effects:

• Filters can reduce pollutants, such as nitrous oxide and sulphur.
• Low-sulphur coal can also be used to reduce sulphur emissions.
• Large forests should be protected because they remove C02 from the air.

7.3. Climate change.
This situation has negative effects on the envinment, and the most serious is climate change, a problem that is associated specifically with fossil fuels. Our use of fossil fuels generates air pollution, such as carbon monoxide gas and heavy metal particles in the air.

• These gases contribute to the greenhouse effect, which increases the Earth's average temperature.
•  We can observe some of the effects of global warming, such as the melting of our polar ice caps and glaciers lead to rising sea levels.
• These pollutants combine with water vapour in the air to produce acid rain.

7.4. Energy consumption.

 The fossil fuels that consumers use in their cars or home heating systems also have an effect on the environment.