Question

Describe the construction of direct current dynamo drawing labelled diagram. Explain its working. What is the difference between direct current and alternating current? Explain it.

Answer 1

Hint: Direct Current Dynamo is similar to an Alternating Current generator but there is a system to counter the effect of changing current direction which is there in an Alternating Current generator. So, we construct an Alternating Current generator and add the system to counter the effect of changing direction of current.

Complete answer:
A well labelled diagram of a DC dynamo.

When the coil rotates, the magnetic flux through the coil changes and an electric current flows through the coil and reaches the commutator and passes onto the wires to carry the current to be used in electric devices through brushes. The commutators are attached to coil and when side of the coil that was on the left initially reaches the right side, the direction of flow through the coil reverses and but due to commutator and brush arrangement the current flow through the wires remains the same and we get direct current in the wire. The energy required to rotate the coil must be provided externally.

Following are the differences between Direct Current and Alternating Current.

Direct Current (DC)	Alternating Current (AC)
Steady flow of current.	Current changes its direction of flow periodically.
Constant potential difference applied.	Potential difference varies with a sinusoidal wave.
Unsafe to transfer over large distances.	Safer to transfer over large distances.
Heavy losses on transfer over long distances.	Losses for transfer over long distances are very low.

Note:
It must be taken care of that the brush and the commutator are not connected to each other but are just in contact to transfer current. The current that we get from this Direct Current dynamo is not perfect but there are some variations, but the direction of current flow remains the same.