Tuesday, 15 March 2011

Direct Current Circuit-(DC)

Direct Current (DC)

Direct Current (DC) is the flow of current in one direction. A basic DC circuit is illustrated as below

Quantities And Units (part-1)

a) Charge (C)

1. Electrical Charge is created when proton and electron charges are separated - it's static.
2. Proton are positively charged particles, while electron are negatively charged particles.
3. Electrical charge is measured in coulomb. One coulomb is the total charge of 6.25 X 10^18 electrons.
Formula :

Q = I X T

b) Current (I)

1. Current is the movement of charge from one point to another in a uni of time.
2. There are two ways of defining the flow of current; first, the conventional current flow and second, the    
    electron current flow. Refers to an illistrated as in figure below;

3. Formula :
I = V/R

Effects Of Electrical Accidents

There are four type of electrical effects:

1. Electrical Shock:

a) 1mA

Mild electric shock.

b) 10mA

Severe electric shock that causes burns and loss of muscles control.

c) 100mA & higher

Electric shock that could be fatal.

2. Burns:

a) First degree burns

sign of redness on the skin can be seen.

b) Second degree burns

Skin to swell and contain liquid.

c) Third degree burns

Reach inside the body and can causes failure of muscular function.

3. Fire

a) Class A fire

Involves organic-based solids such as wood, paper, fabric, and other organic materials

b) Class B fire

involves liquid such as petrol, oil, diesel, turpentine.

c) Class C fire

Caused by gases such as methane and butane.

d) Class D fire

metal-based fire.

4. Explosions

There are several components in the workshop that may explode if they are wrongly connected to power source. A powerful explosion can cause fire.

Important Of Safety

1. Safety precaution is an important aspect in the use of electrical appliances.
2. A safe enviroment is necessary to avoid loss of life and damage to property.
3. Accident result from carelessness, equipment malfaunction and not adhering to safety rules.

Personal Safety

a) Clothing:

1. Wear workshop uniform.
2. Wear insulated,low-heeled shoes.
3. Do not wear any jewellery.

b) Attitude:

1. Report all breakdowns of equipment.
2. Inform the teacher for accident.
3. Plan activities before begin work.

c) Physical condition:

1. Physically fit.
2. Not eye sleepy.
3. Have good eyesight and hearing.

Safety Tool & Equipment

a) Insulation:

Method of protecting, covering and isolating electrical conductors using insulators to prevent the electrical current from flowing.

b) Earthing:

Method of connecting metal parts in an electrical circuit to the ground.

c) Protective device:

A device that reacts by disconnecting the circuit when there is an over flow of current

Safety Workshop & Enviroment

Workshop rules:

1. Ensure workshop has good qeration
2. Ensure workshop has enought lighting.
3. Ensure the workshop heat and clean.

Generation, Transmision, And Distribution Of Electricity

There is two types of electricity generation which are:

a) Direct current generation:

Current that flows through a circuit in one direction is called directed current.

b) Alternating current generation:

Current that is constantly changing its direction of flow, with regards to the polarity of the current source, is called alternating current.

Alternating Current Generation.

there is some types of  power station:

a) Hydro Power Station:

b) Thermal Power Station:

c) Gas Power Station:

Electricity Transmission.

Electricity Distribution.

Consumer Circuit.

Consumer circuit purposes:

a) To ensure the safety of consumers from accidental electric shock.

b) To prevent fire due to electrical faults.

Scematic diagram for a single-phase supply curcuit.