Question

Discuss how electrical "safety" systems and/or devices that are installed into homes and/or appliances "work”. Be detailed and specific in their design and purpose. Describe and explain theories as to how the earth's magnetic field "works", and what effects the field has. Be clear and specific

Answer 1

How electrical safety systems are installed into home and apliences work :

Electricity has two hazards. A thermal hazard occurs when there is electrical overheating. A shock hazard occurs when electric current passes through a person.

  

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   Fig-1 : A simple AC circuit with a voltage source V

and a resistance R.

This circuit has no safety features.

Case of appliance Black (hot) Circuit breaker R White (neutral) Green (ground) Alternate return path through earth

Fig 2 : The three-wire system connects the neutral wire to the earth at the voltage source and user location.

Descriptions : The wiring system used at present for safety reasons, with live, neutral, and ground wires. The three wire system has zero volts and supplying an alternative return path for the current through the earth.The two ground connections on the neutral wire force it to be at zero volts relative to the earth. The neutral wire is the return path for the current to follow to complete the circuit. Furthermore, the two ground connections has an alternative path through the earth, a good conductor, to complete the circuit. The third ground is to the case of the appliance, through the green ground wire, forcing the case, too, to be at zero volts. The live or hot wire supplies voltage and current to operate the appliance.

Also there is a circuit breaker or fuse protects against thermal overload and is in series on wire.

Working Principle :

# The fuses work on the principle of the heating effect of the current. Fuse is always connected in series with the electrical circuit. When the excessive current or heat is generated due to heavy current flows in the circuit, the fuse melts down due to the low melting point of the element and it opens the circuit.

# The AC current in appliances can induce an emf on the case. If grounded, the case voltage is kept near zero, but if the case is not grounded, a shock can occur.

# A ground fault interrupter (GFI) prevents shock by detecting the loss of current to unintentional paths.When live and neutral currents are not equal, it is almost always because current in the neutral is less than in the live wire. Then some of the current, again called a leakage current, is returning to the voltage source by a path other than through the neutral wire and it  goes safely to ground through an intact ground wire.

# Isolation transformers prevent the risk of electric shock by uniting a vessel to the electric power source. Their function is to put a large resistance between the original voltage source and the device being operated.  The appliance is isolated from the original voltage source by the high resistance of the material between the transformer coils. For current to flow through the person, it must pass through the high-resistance material between the coils, through the wire, the person, and back through the earth—a path with such a large resistance that the current is negligible.

How earth magnetic field work :

We all know that a rotating electric current creates a magnetic field.

On Earth, flowing of liquid metal in the outer core of the planet generates electric currents. The rotation of Earth on its axis causes these electric currents to form a magnetic field.

Earth's magnetic field is approximately a magnetic dipole, with the magnetic field S pole near the Earth's geographic north pole and the other magnetic field N pole near the Earth's geographic south pole. See the fig belpow

Geographic North Pole .S CO Compass points North Geoche Magnetic North Pole South Pole N. Magnetic South Pole www.explainthatstuff.com

Effects of the field :

if we fired a beam of electrons into the magnetic field the electrons would deflected by the field. The Earth’s magnetic field does a similar job. The charged particles in cosmic rays are deflected by the magnetic field and many are prevented from hitting the atmosphere directly. Otherwise it would strip away the ozone layer that protects the Earth from harmful ultraviolet radiation.

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Case of appliance Black (hot) Circuit breaker R White (neutral) Green (ground) Alternate return path through earth

Geographic North Pole .S CO Compass points North Geoche Magnetic North Pole South Pole N. Magnetic South Pole www.explainthatstuff.com