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Matter, Materials, and Energy - Electricity: Magnetic and Heating Effects

Grade 3CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Electricity is a form of energy that flows through a closed path called a circuit.

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The Heating Effect of electricity occurs when an electric current passes through a high-resistance wire, causing it to become hot. This is used in appliances like electric irons and toasters where Electrical Energy→Heat Energy\text{Electrical Energy} \rightarrow \text{Heat Energy}.

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The Magnetic Effect of electricity occurs when an electric current flowing through a wire creates a magnetic field around it. A coil of wire wrapped around an iron nail becomes a temporary magnet called an ElectromagnetElectromagnet when current flows.

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Materials that allow electricity to pass through them are called Conductors (e.g., CopperCopper, SilverSilver, IronIron), while materials that do not allow electricity to pass are called Insulators (e.g., RubberRubber, PlasticPlastic, WoodWood).

📐Formulae

Electrical Energy→Heat Energy\text{Electrical Energy} \rightarrow \text{Heat Energy}

Electric Current+Coiled Wire=Magnetic Effect\text{Electric Current} + \text{Coiled Wire} = \text{Magnetic Effect}

Total Energy=Useful Energy+Wasted Energy (Heat)\text{Total Energy} = \text{Useful Energy} + \text{Wasted Energy (Heat)}

💡Examples

Problem 1:

Why does the thin wire (filament) inside an electric bulb glow when the switch is turned on?

Solution:

Due to the heating effect of electricity.

Explanation:

When electricity passes through the thin filament, it encounters resistance, making the wire extremely hot. This heat causes the filament to glow and produce light, demonstrating the transformation of energy.

Problem 2:

What happens to a compass needle if it is placed near a wire carrying an electric current?

Solution:

The compass needle will deflect (move).

Explanation:

The electric current flowing through the wire creates a magnetic field. Since the compass needle is a small magnet, it reacts to the magnetic force produced by the electricity.

Problem 3:

If a circuit is broken by a piece of PlasticPlastic, will the bulb glow?

Solution:

No, the bulb will not glow.

Explanation:

PlasticPlastic is an insulator and does not allow the flow of electric current. Therefore, the circuit becomes 'open' and the energy cannot reach the bulb.