Question

What is the frequency of $220V$ DC voltage?
A.Zero Hz
B.$50Hz$
C.$60Hz$
D.$220Hz$

Answer 1

Hint: Current comes in two variations, namely, DC which stands for direct current and AC which stands for alternating current. We shall analyze both types of currents to understand their working and effect on our daily life. Further, we shall also find the frequencies of both the currents coming to our household.

Complete answer:
Alternating current is the one where the current keeps changing its direction continuously. Once the current flows in clockwise direction in the circuit and the other second current flows in the anti-clockwise direction. The electrons inside the wire keep going back and forth. The bulb connected to AC flickers 100 times a second. This is because in India the current we get from our main supply changes in direction 100 times a second. Therefore, the number of cycles the current through in one second is 50, that is, the frequency of AC is 50 cycles per second or 50 Hertz.
Direct current is one-directional current. The electrons inside the wire move in the same direction with the same speed. Since the current value remains constant, therefore we see that a bulb lighting up due to DC keeps glowing with the same amount of brightness constantly all the time. The batteries we use provide this kind of current.
Direct current flows only in one direction and has no frequency. Therefore, the frequency is equal to zero hertz.

Therefore, the correct option is (A) Zero Hz.

Note:
The bulb lighting up due to AC keeps flickering because before their direction every second, the electrons stop for a fraction of second and then change the direction of flow. During that fraction of second, the current in the circuit becomes zero and the filament of bulb cools down. Hence, the bulb flickers during that time.