Which instrument converts mechanical energy into electrical energy?
A. Electric motor
B. Electric iron
C. Electric generator
D. Electric oven

Hint- Rotational energy, kinetic energy, potential energy is considered as mechanical form of energies which we often find in energy conversions. Wind turbines, peloton wheels, rotary turbines are few examples which are used to convert mechanical energy into electrical energy.

Step-By-Step answer:
The conversion of mechanical energy into electrical energy is done using the principle of faraday's laws of electromagnetism. That is when a coil is moved in a uniform magnetic field a current is induced in that coil in the opposite direction to cancel out the flux that is induced in that coil.
And the device which uses this principle to operate is known as an Electric generator.
Hence the correct option is “C”.

Additional information-
The alternators used at the hydroelectric power plants. They are coupled with the water turbine. Water turbine uses the water pressure to move the turbine. The potential energy of the water is converted into rotational energy by making it to fall the blades of the turbine from a certain height which makes the turbine to rotate. The turbine shaft is connected to the alternator shaft and thus as the turbine rotates side by side the alternator rotates.
Inside the alternator using electromagnetism principles the electrical power is generated and is further transferred from power plant to substation using transmission lines.

Note- The word generator is a misnomer because it only converts one form of energy into another form but no energy is being generated. The same device can be used as a motor that will convert the electrical energy into mechanical energy if it is supplied with electrical power. The generator is also known as an alternator.