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Electricity: Magnetic and Heating Effects - Heating Effect of Electric Current

Grade 6CBSE

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

🔑Concepts

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The heating effect of electric current occurs when an electric current flows through a wire, causing the wire to become hot. This happens because the electrical energy is converted into heat energy.

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A 'heating element' is a coil of wire found in appliances like electric heaters and geysers. These elements are often made of materials like Nichrome, which have high resistance to current flow.

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The amount of heat produced in a wire depends on three main factors: the material of the wire, its length, and its thickness (cross-sectional area).

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In an electric bulb, the filament (usually made of Tungsten) gets heated to such a high temperature that it begins to glow and emit light.

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An Electric Fuse is a safety device based on the heating effect of current. It contains a wire with a low melting point that melts and breaks the circuit if the current exceeds a safe limit, preventing fires and damage.

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Modern alternatives to fuses include Miniature Circuit Breakers (MCBs), which automatically switch off when current in a circuit exceeds the safe limit.

📐Formulae

H=I2×R×tH = I^2 \times R \times t

P=V×IP = V \times I

R=VIR = \frac{V}{I}

💡Examples

Problem 1:

Why is Tungsten used as the filament in an electric bulb rather than Copper?

Solution:

Tungsten has a very high resistance and a very high melting point (approx 3422∘C3422^\circ C).

Explanation:

According to the heating effect, heat H∝RH \propto R. Since Tungsten has high resistance, it produces enough heat to reach a temperature where it glows white-hot without melting. Copper has low resistance and a lower melting point, so it would melt before glowing.

Problem 2:

An electric heater is connected to a circuit. If the current II flowing through the element is doubled, what happens to the heat HH produced, assuming resistance RR and time tt remain constant?

Solution:

The heat produced becomes four times the original amount.

Explanation:

Using the formula H=I2RtH = I^2 R t, we see that heat is proportional to the square of the current (H∝I2H \propto I^2). If current is doubled (2I2I), the new heat becomes (2I)2=4I2(2I)^2 = 4I^2, which is 44 times the original heat.

Problem 3:

What is the primary function of a fuse wire in a household circuit?

Solution:

To act as a safety break in the circuit.

Explanation:

The fuse wire is made of an alloy with a low melting point. When the current II increases excessively, the heat HH produced (calculated by H=I2RtH = I^2 R t) melts the wire, breaking the circuit and preventing electrical fires.