Question

A cycle dynamo works on the principle of

• A. Chemical effects of current
• B. Magnetic effects of current
• C. Electromagnetic induction
• D. Mechanical effects of current

Answer 1

The correct option is C

Electromagnetic induction

The explanation for the correct option

A: Electromagnetic induction

1. According to Faraday's law, “whenever magnetic flux linking on a conductor changes, induced emf (electromotive force) is produced”.
2. Induced emf produces an electric current in the conductor.
3. The phenomenon of producing induced emf or electricity in a conductor due to changing magnetic flux is called “electromagnetic induction”.
4. When the coil of the dynamo rotates, the magnetic flux linking on coil changes and consequently electricity is produced in the dynamo by the phenomenon of “electromagnetic induction”.
5. Faraday's law of electromagnetic induction also states that “induced emf is produced only up to that much period during which magnetic flux linking on the conductor changes”.
6. Electricity is produced by the dynamo only when the magnetic flux falling on the coil of the dynamo changes which is possible when the coil of the dynamo rotates.
7. Below is the diagram showing a dynamo and the magnetic flux falling on its coil.

The explanation for the incorrect options

A: Chemical effects of current

1. When electric current passes through electrolytes (conducting solutions), some chemical change occurs in the solution and this phenomenon is called the chemical effects of current.
2. No chemical is used in dynamo, hence, the working principle of a dynamo cannot be based on the chemical effects of current.

B: Magnetic effects of current

1. When current flows through a conductor, a magnetic field is developed around it and this phenomenon is called the magnetic effect of current.
2. No external current is applied to the dynamo, and the magnetic field is developed only when an induced current flows through the dynamo.
3. Magnetic effects of current has nothing to do with the working of the dynamo.

C: Mechanical effects of current

1. Generation of mechanical energy in the appliances like motors, fans, etc due to the flow of electric current through them is called the mechanical effect of current.
2. No external current is applied to a dynamo that could generate mechanical energy in the dynamo.
3. Mechanical effect of current cannot be the working principle of a dynamo because in a dynamo current is generated itself and for the phenomenon of the mechanical effect of current, an external current is required which is not the case with a dynamo.

Hence, option (C) is correct.