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Electricity: Magnetic and Heating Effects - Conductors and Insulators

Grade 6CBSE

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

🔑Concepts

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Electric Conductors: Materials that allow electric current to pass through them easily. Most metals like Copper (CuCu), Aluminum (AlAl), and Iron (FeFe) are good conductors.

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Electric Insulators: Materials that do not allow electric current to pass through them. Examples include rubber, plastic, wood, and glass.

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Heating Effect of Electric Current: When an electric current flows through a wire, the wire gets hot. This is known as the heating effect. This effect is utilized in devices like electric heaters, irons, and geysers.

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Electric Fuse: A safety device based on the heating effect. It contains a wire with a low melting point that melts and breaks the circuit if the current (II) exceeds a safe limit.

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Magnetic Effect of Electric Current: When electric current flows through a wire, it behaves like a magnet. This was first observed by Hans Christian Ørsted using a compass needle.

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Electromagnets: A coil of insulated wire wrapped around a piece of magnetic material (like soft iron) acts as a magnet when current flows through it. The magnetic strength increases with the number of turns (nn) and the current (II).

📐Formulae

H=I2RtH = I^2 R t

V=I×RV = I \times R

P=V×IP = V \times I

💡Examples

Problem 1:

An electric heater is connected to a power supply. If the resistance of the heating element is R=50 ΩR = 50 \, \Omega and the current flowing through it is I=2 AI = 2 \, A, calculate the heat produced (HH) in t=10 st = 10 \, s.

Solution:

H=I2Rt=(2)2×50×10=4×50×10=2000 JH = I^2 R t = (2)^2 \times 50 \times 10 = 4 \times 50 \times 10 = 2000 \, J.

Explanation:

By applying the formula for the heating effect of current (H=I2RtH = I^2 R t), we find that 20002000 Joules of heat energy is generated.

Problem 2:

Why are the handles of screwdrivers used by electricians usually made of plastic or rubber?

Solution:

Plastic and rubber are insulators.

Explanation:

Insulators do not allow electric current to pass through them. Since the human body is a conductor, using tools with insulating handles protects the electrician from electric shocks while working on live wires.

Problem 3:

What happens to a magnetic compass needle placed near a wire when the switch is turned 'ON'?

Solution:

The compass needle shows deflection.

Explanation:

This happens due to the magnetic effect of electric current. The current-carrying wire creates a magnetic field around it, which exerts a force on the magnetic needle of the compass, causing it to move from its North-South position.

Conductors and Insulators - Revision Notes & Key Formulas | CBSE Class 6 Science