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What is the heating effect of electric current? Give its uses.

Class 8 ScienceNCERT chapter: Electricity: Magnetic and Heating Effectsइसे हिंदी में पढ़ें

Exam-ready answer

When an electric current flows through a wire, the wire becomes hot. This is called the heating effect of electric current. The heat produced depends on the material, length and thickness of the wire and on the current. It is used in electric heaters, irons, toasters, kettles, geysers and in electric fuses that protect circuits.

Explanation

In a simple activity, a thin wire is connected to a cell and a switch. When the switch is closed for a short time and the wire is touched carefully, it feels warm. When the switch is opened, the wire cools down. This shows that an electric current produces heat in the wire through which it flows.

The amount of heat depends on the wire. Appliances such as heaters, irons and toasters have a coil of special wire called the element, usually made of an alloy called nichrome, which becomes very hot and even glows red. The connecting copper wires stay cool. In an old filament bulb, the thin filament becomes so hot that it gives out light.

An electric fuse is a safety device based on the same effect. It has a wire made of a material that melts at a low temperature. If too much current flows because of a fault, the fuse wire heats up, melts and breaks the circuit, which prevents fires and damage to appliances. Heating is wasted energy in devices like fans and computers, which is why they get warm.

Points to remember

  1. Heating effect: a wire gets heated when an electric current passes through it.
  2. Heat produced depends on the material, length and thickness of the wire and the amount of current.
  3. Element: the coil of wire (often nichrome) in heaters, irons and toasters that gets very hot.
  4. Electric fuse: a safety device whose wire melts and breaks the circuit when too much current flows.
  5. Uses: room heater, electric iron, toaster, kettle, geyser, filament bulb and fuse.

Exam tip

Define the heating effect in one line, then list at least four uses, and mention the electric fuse separately as a safety use — examiners often look for it.

Questions students also ask

Why is a fuse wire made of a material that melts easily?
A fuse must break the circuit quickly when the current becomes too high. Its wire is made of a material with a low melting point, so the extra heat melts it before the wiring or appliances get damaged.
Why do the connecting wires of a heater not glow while its element does?
The element is made of an alloy like nichrome that produces a lot of heat when current flows. The connecting wires are made of copper, which produces much less heat, so they stay comparatively cool.
Is the heating effect always useful?
No. In devices like fans, mobile chargers and computers, the heat produced is unwanted and wastes electrical energy. That is why such devices have vents or fans to remove the extra heat.

Chapter labels help you find the topic in your textbook. Check your own edition: chapter names and order can change. These are Know.it explanations, not official NCERT solutions.