Electric torch or Flashlight

A torch is a portable handheld electric light. A typical torch consists of a light source mounted in a reflector, a battery and a switch.
The source of light is an LED ie light emitting diode. In LED the longer leg is positive end and the shorter leg is negative end. It is a diode that allows current to flow only from positive end  to negative end.

A dry cell converts stored chemical energy into electrical energy. Two or more cells form a battery.A dry cell is a zinc carbon cell.It produces voltage of about 1.5 volt. Zinc container act as negative electrode, carbon rod acts as positive electrode.The electrolyte used is a moist paste of ammonium chloride and zinc chloride. It is made up of metallic cylinder. It has a flat case and metal cap on top.The metal cap is positive end of cell and flat base is negative end of cell.

The switch is an electric device that is used to make or break the circuit.

Due to chemical reaction within the battery, the negative electrode build up an excess of electrons. When the cicuit is closed with a conductive path, the electrons are able to travel to the positive end.Thus in turn provides power to LED.Inside the LED the electrons recombine with the holes and energy is released in the form of light.

When the switch is in off position, the circuit is not complete and the current doesnot flow through it. Such circuit is called an open circuit.When switch is in On position the circuit is complete and current flows through it. Such circuit is called closed circuit.

DIY parachute

Parachute

A parachute is a device used to slow down an object that is falling towards ground..parachutes are generally made out of light strong nylon.The word parachute comes from French words para and chute meaning " to shield a fall".

When a person is falling two forces act on him 1. Gravity (acting downwards) and 2. Air resistance(acting upwards) But here the gravitational pull is more than air resistance. So the person speedily falls on ground whereas with parachute, the air resistance increases due to larger surface area of the canopy of parachute. Hence, this slows down the parachute and the person can safely land on the ground.

Steps:

FACTS
Larger the surface area, greater is the air resistance and slower the parachute falls.

Making a tiny hole in the center will aid in to fall straight down without oscillation.

If the weight is less the parachute doesn't work.
If the weight is more, the parachute comes down quickly.
Hence

Uses of parachute:
1. Paragliding
2. Military
3. Airplanes

Main parts of parachute:
1. Pilot chute: a small parachute that opens main parachute
2. Vent or apex: allows slow escape of air to pass from main parachute
3. Canopy: main part of parachute
4. Suspension lines: spreads the weight of parachutist evenly across the canopy
5. Risers:connects the links to harness

Working of real parachute:
There are three parachute in a container, main parachute, reserve parachute and pilot chute. Once you trigger pilot chute it opens up creating force that tugs out the main parachute. Reserve parachute is used if the main parachute fails to open.