Question

1.why DC current flows in one direction only?
2.Why can't we step up or step down a DC current?
3. Why can't we step up or step down a DC current using a transformer?
4.Why there will be power loss if DC is travelled for a long distance?
5. Which is dangerous AC or DC and why?​

Answer 1

Answer:

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Answer 2

Answer:

1. The AC current is produced using generators (or turbines) in which the armature of the rotating coil reverses its direction of rotation after each half rotation due to the use of split rings commutators in such generators. As a result, the change in the direction of of rotation of the armature 50 times a second, i.e., 50 Hz translates to the change in the direction of AC current at the same frequency of 50 Hertz. On the other hand DC current is not produced using generators so there is no such change in its direction.

2. The stepping up or stepping down of AC current involves the change in the magnetic flux linked with the primary coil of a transformer and the change in magnetic flux is ultimately due to the alternating characteristic of the AC current. If there is no change in the number of magnetic field lines in the primary coil due to change in the direction and magnitude of the current in the primary coil, there will be no change in the magnetic flux, hence, stepping up or stepping down will not be possible. This is the very same case with DC current which does not change its direction and magnitude periodically, hence, there are no magnetic field lines linked with it.

KEYWORDS: Since DC current does not change its direction and magnitude periodically, in a transformer, even if DC current is used, there will be no change in the magnetic flux linked with the primary coil.

3. SAME ANSWER AS ABOVE; SAME KEYWORDS.

4. In case of AC current, the AC voltage can easily be stepped up or step down using a transformer. Stepping up or stepping down the AC voltage results in the decrease or increase in the amount of current respectively. For long distance transmission of AC current, the AC voltage is stepped up so that the amount of current flowing through the transmission line wires decreases. By the relation according to the Principle of Heating Effect of Current,

Heat=I^2 R t

where, I stands for current flowing through the wire per unit time.

Therefore, from the above relation, heat produced in the transmission line wires is directly proportional to the current flowing through the wire per unit time by decreasing the amount of current flowing through the wire the the amount of heat produced and hence, the dissipation of energy is decreased.

On the other hand, in the case of of DC current, the stepping up or stepping down of voltage using transformers is not possible hence, DC current must be transmitted at the same voltage at which it is produced, therefore, the the heating effect will be more and thus, the dissipation of energy (loss of power).

5. Both AC current and DC current are very dangerous depending upon the amount of voltage produced by the power source. For example, a small AAA size battery might not be dangerous at all since it is only 6 volt, however, a very high density battery providing a current at a very high voltage can be as dangerous as AC current at the same voltage. Nevertheless, practically we, the consumers, do not deal with a DC source with so high voltage rating. So, it is generally AC current, which is more dangerous due to its availability at very high voltages.

HOPE THIS ANSWER HELPS YOU TO THE FULLEST EXTENT.