- Direct current is a uniform current flowing in one fixed direction in a circuit
- Direct current (d.c) is usually supplied by acid-based batteries or dry cells.
- A common example of acid-based (electrolyte) batteries is the car battery.
- Figure below shows the graph of current supplied by a dry cell over time.
- Alternating current is an electric current in which the direction of flow of the electrons reverses periodically
- Alternating current (a.c) is generated from alternating current generators such as hydroelectric power generators.
- The electricity supplied to households is alternating current.
- Household electricity (alternating current) changes direction 50 times every second. Its magnitude also changes with time.
Period And Frequency
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgjQjewfZ_oiHjrI9SY2qBSLureddAeCINM5r2itJ88Di3D55hzQf7ESvOQRqoV5jpHGmgm0qrkMYTs49UN1tYvkfSaUD3XafW5l1Z8Gy0MWCglu-fiRvp1ay690Q6vFegE3T2k3V6FEVQ/s320/graph+period.png)
- The time taken for one complete cycle is known as the period, T.
- The frequency f is defined as the number of complete cycles in 1 second.
- The relationship between the frequency and the period is:
- In SPM, you need to know the effect of both the direct current and alternating current on
- a bulb
- a capacitor
- a moving coil loudspeaker
- Table below give the summary of the comparison of the effect of direct current and alternating on a bulb, a capacitor and a moving coil loudspeaker.
Direct Current | Alternating Current | |
Effects on a bulb | The bulb lights up | The bulb lights up |
Effects on a capacitor | Current is detected at the very beginning and then ceased to become zero afterward. | Current is detected |
Effects on moving coil loudspeaker | No sound produced | Sound produced |