19 January 2014

The Heating Effect of Electric Current : Science

Heating Effect of Electric Current

In the 19th century, James Joule studied a property, which says that "when an electric current flows through the filament of a bulb, it generates heat, and so the bulb becomes hot". This property is named the heating effect of electric current.

Must Read :  Electric Components
Compact Fluorescent Lamps (CFL's)
We use electric bulbs to obtain light. Due to the heating effect, some part of the energy received by the bulb is used up, and hence, some electricity is wasted. CFL’s do not depend on the heating effect of electricity to produce light, since they do not use filaments.   Using CFL’s instead of ordinary bulbs minimises wastage of electricity. In CFL’s, light is generated using two electrodes. The fluorescent coating inside each tube makes the light brighter.
We use every day many appliances that work on the property of the heating effect of electric current. For example, the electric room heater, electric roti maker, electric iron, toaster, hair dryer, electric stove, immersion water heater, food warmer, electric coffee maker, electric rice cooker and geyser work on the property of the heating effect of electric current.

Heating Elements

The Heating Effect of Electric Current, CBSE Notes, NCERT Notes
These appliances have coils of wire that produce heat, which are known as heating elements. As current flows through these electrical appliances, the coils of wire inside turn bright orange red in colour. This is because a huge amount of heat is produced. Different appliances have different types of heating elements. The type of heating element depends on the function of the appliance. Some appliances are required to produce more heat than others.

ISI Mark

You should purchase only appliances that bear an ISI mark. ISI stands for Indian Standards Institute. If an appliance bears the ISI mark, it means that it is safe and will not waste electrical energy. Moreover, it is a mark of quality.

Factors affecting production of heat

The factors that affect the production of heat in a wire through which an electric current is passing are the length and thickness of the wire, the duration of flow of current, and the material of the wire.

Electric Fuse

The electric fuse works on the principle of the heating effect of electric current. An electric fuse is a safety device to prevent damage to an electrical circuit when excessive current flows through it. It is made of a special material. As the current increases beyond a limit, the wire in the electric fuse melts and breaks off. The fuse is then said to have blown off. The circuit is broken and current stops flowing through it. Thus, a fuse prevents fires. 
There are various types of fuses. Some fuses are used only in buildings, while others are used in appliances.

Reasons for Excessive Current

When all the appliances are connected to the same socket, these appliances draw more current, and so the load increases.
When the insulation on the wires is torn, two wires carrying current touch each other directly. This causes a spark, which leads to fire. This is termed as a SHORT CIRCUIT.
If a fuse is not used, then overloading and short circuits result in fire.

Miniature Circuit Breakers (MCB)

Instead of fuses, MCBs are used nowadays because these are switches that turn off automatically when there is an overload or a short circuit. After solving the problem in the circuit, the switch can be turned back on, and then the current flows as usual.

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