Which of the following does Not use magnetic effect of current to function?

Analysis of the Question

The question asks us to identify which of the listed devices does not rely on the magnetic effect of an electric current to operate. The magnetic effect of current (electromagnetism) occurs when an electric current flowing through a conductor creates a magnetic field around it.

Explanation of Concepts

• Magnetic Effect of Current: This principle is used in devices where an electric current is converted into mechanical motion or sound through the interaction of magnetic fields.
• Electrochemical Effect: Some devices function by storing or converting chemical energy into electrical energy (or vice versa) through chemical reactions, rather than using magnetic fields.

Step-by-Step Evaluation

1. Lead acid accumulator (Option A): This is a type of rechargeable battery. It stores energy through chemical reactions (electrochemical process) between lead plates and sulfuric acid. It does not use magnetism to store or release energy.
2. Electric bell (Option B): An electric bell uses an electromagnet. When current flows, the electromagnet attracts a hammer to strike the bell. This is a direct application of the magnetic effect of current.
3. Moving coil galvanometer (Option C): This device measures small electric currents. It works by placing a current-carrying coil in a magnetic field, which experiences a torque (turning effect). This is a classic application of the magnetic effect of current.
4. Telephone receiver (Option D): A telephone receiver uses an electromagnet to convert varying electrical signals into mechanical vibrations of a diaphragm, which produces sound. This also relies on the magnetic effect of current.

Conclusion

Comparing these, the lead acid accumulator is the only device that functions based on chemical principles rather than the magnetic effect of an electric current.

Exam Tip: Whenever you see questions about "effects of current," remember the three main categories:

• Heating effect: Electric iron, kettle, filament bulb.
• Magnetic effect: Electric bell, motor, galvanometer, transformer.
• Chemical effect: Electrolysis, electroplating, lead-acid batteries (accumulators).