Question

On what principle, a D.C generator is based upon?
${\text{A}}{\text{.}}$ Magnetic effect of current
${\text{B}}{\text{.}}$ Lighting effect of current
${\text{C}}{\text{.}}$ Electrochemical induction
${\text{D}}{\text{.}}$ Electromagnetic induction

Answer 1

Hint: Here, we will proceed by defining a D.C generator along with the function it serves. Then, we will discuss the operating principle on which it works. Then, we will also discuss the rule for determining the direction of the induced current.

Complete step-by-step answer:

A D.C generator is an electrical machine that transforms mechanical energy into direct electrical current. This energy conversion is based on the principle of dynamically induced electromotive force (emf).

D.C generator's operating principle:

If a conductor is situated in a changing magnetic field (or a conductor is placed in a magnetic field), an electromotive force (emf) is produced in the conductor according to Faraday's electromagnetic induction laws. The magnitude of induced emf can be computed from the D.C generator emf equation.
If a closed path is given for the conductor, the induced current will flow within the path. Field coils generate an electromagnetic field in a D.C generator, and the armature conductors are rotated into the field. Therefore, the armature conductors produce an electromagnetically induced emf. Fleming's right hand rule provides the direction of induced current.
According to Fleming’s right hand rule, the direction of the induced current varies every time the conductor's direction of motion varies.

In an armature spinning in the clockwise direction, and a conductor going upward at the left. When the armature completes a half-rotation, the particular conductor's direction of motion will be reversed to descend. Therefore, the direction of current must change in each armature conductor. But when the current reversal happens, links of the armature conductors often get reversed with a split ring commutator. And so we are having unidirectional current at the terminals.

Therefore, a direct current (D.C) generator is based upon electromagnetic induction
Hence, option D is correct.

Note: There are generally two types of D.C generators including separately excited and self-excited. In a separately excited DC generator, an independent external D.C source energy the field coils whereas in a self-excited D.C generator, the current produced by the generator energizes the field coils.