The device used for producing electric current is called a ______.
A. Motor
B. Generator
C. Galvanometer
D. Ammeter

Hint: In this question we have been asked to name a device from the given options, that produces an electric current. Therefore, to answer this question, we shall discuss the working and working principle of each device given to us in the options. Later, we shall select an appropriate device, which produces an electric current.

Complete step-by-step solution
The first option given to us is a motor. The motor is a device that converts electrical energy into mechanical energy. The principle of motor or electric motor is on the current-carrying conductor which produces magnetic fields around it. The force is generated by placing a current-carrying conductor perpendicular to the magnetic field. Therefore, a motor electric current is used as an input. Therefore, a motor does not generate an electric current.
The second option is a device called a generator. It is a device that converts mechanical power into electrical power. This device works on the principle of electromagnetic induction. The generator uses mechanical energy to force the flow of charge present in the conductor.

Consider the diagram above. The conductor coil along with its core known as an armature is connected to a shaft of a mechanical energy source such as a motor and rotated. The mechanical energy required can be provided by engines, turbines, etc. When the coil rotates, it cuts the magnetic field which lies between the two poles of the magnet. The magnetic field will interfere with the electrons in the conductor and induce a flow of electric current inside it.
Therefore, the generator is a device that generates electricity or electric current.
The device given in options C and D is a galvanometer and ammeter respectively. These are known as measuring devices. The galvanometer and ammeter are the devices used to measure the flow of electric current. They, however, do not generate any electric current themselves.
Therefore, the correct answer is option B.

Note: The measuring instruments galvanometer and ammeter mentioned in option C, are also capable of showing the direction of current flow. The ammeter can measure a small amount of current in the milli and microampere range. The working of both devices is different as well. The electric generator was invented by Charles F. Brush.