Alternating current: this is when electrical current flow in all different directions at any cycles. They flow in power lines and travel from the walls to the homes to provide electricity. In Europe the cycles per second is 50 (frequency of 50 Hz) it’s cheap to change the voltage of the current.
Direct current: this is when electrical current flow in one direction. It’s the current which is used in flash lights or another device which uses batteries.
Dc currents always flow in one direction and can flow through a conductor for example, wires and it can travel through a semiconductor and insulators:Ac current is current which flows in all different direction as shown in the graph sketched below: Task 1cElectric shocks happen when a person gets in contact with high voltage. The effect electric shocks have on people can be harmful for instant, if a person was electrocuted with a very high voltage then it could cause death because the rhythm of the heart would be disturbed or in some cases the current can stop the heart from beating and cause a cardiovascular arrest. Electrical shocks can cause burns. If the voltage was not too high, then burns can be found just on top of the skin. But if a high voltage was to shock a person then it could cause internal burns. Such as burns to the organs that can affect the heart. The burns which are caused by electric shocks can cause organ failure which results in death and if a person was to survive then recovery would be long and painful. Moreover, neurological effect is another factor which can be harmful to the human body. This is when electric shocks disturb the nervous control effecting on heart and lungs. When electric shocks disturb the nervous system, it doesn’t in most cases leads to death but can make a person be unconscious. It also, effects the chest when 50 or 60 Hz is passed through the chest. It results in ventricular fibrillation. This must be treated as soon as possible as it can cause the heart muscle to beat fast and loose its normal rhyme. If too much is passed through the chest then it can stop the heart from beating as soon as it has travelled to the chest.The following are the most common effects of electric shocks:· A person has high chances of collapsing · A person would have high chances of muscle contractions that can cause fractures and loss of consciousness and in some cases, it can cause the joins to dislocate · A person could have a paralyze to the respiratory system and can change the rhythm of the heart or can stop it from beating completely. Tissue that are at the start and end of the current can die.· A persons blood pressure can drop which causes the electrolyte balance to release myoglobin resulting in kidney failure. Fires are mostly started in mains wires (homes, buildings) or due to manufacture failure. Damaged outlets, equipment start fires and old outdated apparatus. Others can be started by problems in cords, receptacles and switches. Cords that have been damaged should not be near floors, curtains and rugs as it is most likely can start off fires. And cords under rugs can cause fires which can be dangerous. Most the fires are started by people who do not follow the instructions of an electrical equipment. Extension leads can cause fire and portable heaters also start fires. The impact that fires have on humans is that it can cause severe burns which can cause the skin of the surface to burn and internal burns can be caused. This causes the body tissues to be scarred which means dead is most likely to occur and then the fibrous tissues are instead replaced with the dead tissue. Dc and Ac:
Ac and dc both are harmful to the body, but the symptoms are slightly different depending on the voltage if it is high then there is more risk than it is low. It also, effects on the amount of current, time of flow and pathway current. It is said to be that ac current is more harmful to a human than dc because more dc currents are needed to make the same harmful effect that ac current would have. This is because more milliamps are required in DC as it is a flow of current in one direction so if a person was to get an electric shock from the hand or feet then it wouldn’t be so bad as it doesn’t cross the heart, but still the person would have a lot of internal burns which could lead to death. With AC it’s not as simple as the current flows in all directions so when a person is electrocuted with AC current then it is most likely the current has been to the heart which can stop the heart from working and lead to death. The series of contraction is dependent on the amount of frequency that is applied to the human body. Also, more milliamps are required from DC current then AC even if it is the same voltage. · To minimise the risk of electric shocks it’s important to reduce the voltage, portable equipment is powered by 110 voltage supply via transformer. Which are tapped on the earth so the max voltage between a live conductor and earth is restricted to 55v. Also, to minimise the risk it is essential to ensure fuses are fitted correctly. A fuse is a device which is made to protect high current. It does this by blowing up or cutting off when the current is increased the rated capacity also increases. Fuses are made for specific equipment, so a fuse should only be used for that equipment. For example, a 3-amp fuses are used in equipment which require around 700 watts. Equipment that require more than that should not be used with a 3 amp plug as it can cause electric shocks or even fires. To avoid any electric shocks, it is important that a person reads the manufactures instructions to avoid any risk to the person itself and the equipment. To avoid any burns or shocks it is important that an extension lead is not overloaded because if it is then there is a high chance of it exploding. When this happens, it can cause an electric shock either from the lead or from the equipment because extension leads are able to take a specific amount of current and when there is an overload it can be harmful for the person. To minimise this risk, it is important that people do not overload the lead and be careful of what electronics can be plugged in. · To avoid starting fires within the socket of an electronic device an earth wire should be used as it is the safety wire which is connected to the earth. It helps prevent fires or any AC/DC current through the external area of the plug. It works by cutting off, when the live parts come across the earth wire then the fuse automatically blows or cuts any supply. Class 1 equipment have this earth wire. Class 2 have plugs which are double insulated and is shown by a double symbol. Class 2 equipment have no earth wires. The device of a class 2 has the basic and extra insulation. Both can stop fires and electric shocks.