RMS Value of Direct Current

RMS stands for root mean square. It is the value of the current or the voltage that is varied. While measuring the RMS in DC current, everything usually depends on the multimeter. In the case of DC current, the true RMS Value is irrelevant because the RMS in a pure DC voltage is the same as its DC value and if the case involves a signal having both DC and AC applied to it, then the multimeter will show the RMS value for the AC part of the signal.

RMS Value

It stands for Root Mean Square. RMS Value is defined as the square root of the mean of the squares of the values of voltage signals which varies continuously. RMS is also known as the quadratic mean value. The RMS value is very important in the case of an AC signal because of the continuous change in the instantaneous value of the AC signal with time. Whereas, in a DC signal, the instantaneous value remains relatively constant and hence cannot be directly used in the calculations. The RMS value is also known as the equivalent DC voltage since the RMS value gives the AC power drawn by a resistor which is similar to the power drawn by a DC source.

Calculation of RMS value

It is calculated only where the magnitude varies w.r.t time. We cannot find an RMS value in a DC waveform as it has a constant value for every time interval

Methods of calculating the RMS value:

There are two ways of calculating the RMS value

1. Graphical 
2. Analytical

Graphical Method-  In the graphical method, the squares of each point are taken, and then their mean is calculated. After calculating the mean, we find its square root, which gives the root mean square value.

Analytical Method- In this method, the RMS value is calculated by a mathematical procedure that involves the use of the following formulas:

• From Peak Voltage (Vp)

            VRMS =12 Vp

• From Peak to Peak Voltage (Vpp)

            VRMS =122 Vpp

•  From average Voltage (VAVG)

           VRMS = 22VAVG

Current is defined into two types AC and DC. AC stands for Alternate Current, where the electric charge changes its direction periodically, whereas, in DC, the charge or we can say the current, flows only in one direction.

DC Current properties

DC cannot travel through a very long distance because it loses electric power. The electrons in DC move forward steadily in a single direction, it has no frequency or zero frequency, and it is much more difficult and expensive to change the voltage of a DC as compared to AC. It is used in electronic devices that use batteries as their source of power. DC is the abbreviation used for Direct Current. In DC, the charge does not change its direction and flows in one direction only. During the 1880s, DC was replaced with the alternating current because it was difficult to convert it to lower or high voltages. It is also not used at homes because DC is considered more lethal as compared to Alternate Current and cannot travel a very long distance, whereas AC can be considered safe while transferring to longer distances.

What is the RMS value of DC?

To calculate the RMS value, we need to consider time. Since DC has no time period and has just a constant power supply. The RMS value is used for measuring the power in an AC system. since we can not measure average AC power using mathematical calculation as it is zero.

Here in one alternating cycle, it rises to maximum power and then drops down to minimum power. So, a mathematical calculation is used for calculating the RMS value whereas, in the case of DC power, we have only simple constant power and no alternate power, which can be calculated easily by multiplying the voltage with the current. 

Application of DC

• Rectifiers 
• Flashlight 
• Refrigerators 
• Doorbells
• Water Pumps
• Alarm Systems

Difference between AC and DC

Characteristics of DC

It has constant polarity and avoids the occurrence of inductance and capacitance. The power factor of DC is 1. There are two types of DC – pure direct current and pulsating direct current,  pure DC has a constant magnitude, but pulsating DC has variable magnitude. The loss of electrical energy is very low in an HVDC (high voltage direct current) transmission system.  It connects with the resistive type of load, and it has resistance as its parameter. It only moves in a  single direction.

The low of DC is unidirectional, and It only moves in a forwarding direction, from positive to negative, and is constant in time. As the direction flow remains the same, it provides constant voltage. The frequency is zero, or it often has no frequency as it does not change direction. 

Conclusion  

The flow of charge in one direction is the defining property of a DC. In the 1880s, it was replaced with AC because of many reasons, one such reason being that it was too difficult to convert it into lower or higher voltages. And studied “what is the RMS value of DC in brief”. We don’t realise it, but we use DC in our daily regime while using the battery charger, the refrigerator, doorbells, and alarm systems use DC for their functioning.