Power Vs Voltage:Comparative Analysis and Facts


This article will discuss power vs voltage in detail, such as the relationship between power vs voltage, reactive power, motor power, power factor, etc.

Comparison between Power and Voltage:

PowerVoltage
Power is the rate of energy absorbed or supplied with respect to time. Voltage is the potential drop between two points.
Mathematical definition of power is the multiplication or product of instantaneous voltage and instantaneous current of a circuit. Mathematical definition of voltage (as Ohm’s Law) is the product or multiplication of resistance and current of a path or branch of a circuit.
P =VI V = IR

Is power equal to voltage?

Voltage is the potential drop between two points, whereas power is the rate of energy absorbed or supplied with respect to time.

The instantaneous (or immediate) power of any circuit can be described as the product of instantaneous (or immediate) current (i) and instantaneous (or immediate) voltage (v). The measuring unit (or component) of power is the watt. Voltage is the electromotive force, and its unit of measurement is Volt.

What is its Relationship to Voltage and Power?

Power is the rate of absorbing and providing energy with respect to time, and its measuring unit is watts.

To define the relationship between power and voltage, from physics, we know that

[latex] p\Delta =\frac{\mathrm{d} w}{\mathrm{d} t} [/latex]

 Where p is power in watt, w is energy in joule, and t is time in seconds.

now, [latex] p =\frac{\mathrm{d} w}{\mathrm{d} t} = \frac{\mathrm{d} w}{\mathrm{d} t} \frac{\mathrm{d} q}{\mathrm{d} t} = vi [/latex]

so [latex] p =vi [/latex]

Here p is the instantaneous power, a varying time quantity, v is the instantaneous voltage, and i is the instantaneous current.

The direction of current and voltage polarity determines the sign of power. When power is in a positive sign, then power is being delivered observed by an element. If the power is in a negative sign, then power is supplied by any element.

According to passive sign convention, the current enters through the positive polarity of the voltage source; when power is positive, which implies the absorbing power, and if power is negative, which means the element is releasing or supplying power.

Power Limit Vs Core Voltage

The terms core voltage and power limit are defined terms for microprocessors.

Power limit is the maximal magnitude of power that can be produced or consumed by the system. In some cases, when power consumption exceeds the specific power limits for the processor, that is when the processor automatically reduces the core frequency in order to minimize the power in its required range.

At the same time, Core voltage is a voltage specifically defined voltage supply to the processor core of a microprocessor. Each microprocessor has a specific range of core voltage, showing that the range of core voltage can vary with the manufacturer or type of microprocessor, which means the manufacturer may configure the processor to use any voltage within the range of the defined core voltage.

Power Factor Control vs Voltage Control

The voltage level can be controlled by controlling the production absorption and reactive power flow in a circuit.

Different devices or methods of controlling voltage search as source or sink of reactive power like

  • Shunt capacitor synchronous condenser.
  • Shunt reactors.
  • Static var compensators. 
  • Line reactance compensators such as series capacitors. 
  • Induction regulators.
  • Tap changing transformers.

Power factor control can be used to increase the power factor load, improving the efficiency of distributing system. For power factor control, inductors, capacitors, rectifiers, etc., can be used.

There is specific equipment that is used for power factor control. Those are:

  • Static capacitors,
  • Synchronous condenser,
  • Phase advancer.

Power Loss Vs Voltage Drop

Voltage drop is the fall or decrease in electric potential in a circuit, whereas power loss is the wastage of electrical energy.

Voltage drop in a circuit is generally caused by the resistance of the current flow through a conductor, or a wire is any length or size of wire that has some resistance. And current running through the wire causes the voltage drop as the length of the wire increases, resistance increases, resulting in a considerable voltage drop in the circuit. At the same time, power loss can be caused by any failure in the circuit or due to the low efficiency of the overall circuit. Power loss is generally caused by a short circuit, cascading failure, fuse, noise, unwanted power dissipation, etc.

The voltage drop across a circuit can be determined by the value of the impedance of the overall circuit. At the same time, the power loss in a circuit can be determined by the difference in input and output power of the circuit.

As the voltage increase, all current increases through the circuit, which can cause more power loss across any component or wire of the circuit.

power vs voltage
Image Credit: “High Voltage” by ElleFlorio is licensed under CC BY-SA 2.0

Power DB Vs Voltage DB

Voltage or power gain, or any gain in electronic can be defined in db.

Voltage gain in terms of DB (means decibels) can be defined as the difference between the output voltage level ( or input electric potential level) in decibels in the input voltage level ( or output electric potential level)  in decibels. 

The value is also equal to the 20 times of standard log of the ratio of output voltage ( [latex] V_out [/latex] ) to the input voltage ( [latex] V_in [/latex] ).

[latex] db= 20 log10 \frac{v_o}{v_i} [/latex]

Where [latex] v_o [/latex] is the output voltage and vi is the input voltage

A power gain in DB can be described as the difference between the power generated in the circuit’s output in decibels and the input power to the circuit in decibels.

The value of power gain is equal to 10 times of the common logarithm of the ratio of power generated at the output of the circuit to the input power to the circuit.

[latex] db= 10 log10 \frac{p_o}{p_i} [/latex]

Where [latex] p_o [/latex] is the power generated at the output of the circuit.

And [latex] p_i [/latex] is the input power to the circuit.

Power Gain Vs Voltage Gain

Sometimes, Power gain cannot be clear in terms in terms of input power and output power.

The power gain of a circuit can be described as the ratio of output power generated to input power applied to the circuit. The voltage gain can be defined as the ratio of output voltage produced in the circuit to the input voltage applied to the circuit.

Power Amplifier Vs Voltage Amplifier

The amplifier is a device that is used to increase or boost the overall power of a signal.

A voltage amplifier is used to elevate the voltage level (or electric potential level) at the output of the amplifier. It is also going by the name of a small-signal amplifier. The coupling used in this amplifier is RC coupling. Whereas a power amplifier is used to rise up the power level at the output of the amplifier, this amplifier is also recognized as a large signal amplifier. The coupling used in this amplifier is transformer coupling.

The magnitude of the input signal of the power amplifier is comparatively more extensive than that of the input signal of a voltage amplifier. The value of Beta of any power amplifier is much higher than that of a voltage amplifier. Heat dissipation at a power amplifier is higher than that of a voltage amplifier. The load impedance is relatively higher for a voltage amplifier than a power amplifier.

Power Conditioner Vs Voltage Regulator

A power conditioner is a device that protects the device against power surges or spikes.

A power conditioner is mainly used to improve the quality of power which is about to deliver to load equipment. Commonly, a power conditioner also come up with electromagnetic interference (EMI) and radio frequency interference  (RFI) filtering.

The voltage regulator is a device used to maintain the voltage at a constant value or within a predefined range. A lower voltage or over voltage can affect the performance or health of the electronic devices.

In some cases, a power conditioner can be designed with a voltage regulator along with other circuits which perform at least one other function to improve power quality, such as noise separation, power factor correction, transient impulse protection, etc.

Dynamic Power Vs Voltage

The total power dissipation of a CMOS circuit is a summation of dynamic and static or leakage power dissipation.

Dynamic power is referred to the component of total power dissipation of the CMOS circuit when the CMOS circuit changes its logic state from one logic to another. Dynamic power is the function of supply voltage switching frequency and the output load of the transistor.

Dynamic power dissipation in the relation of the supply voltage can be defined as 

[latex] P = CV^2 f  [/latex]

Where V is the supply voltage and f is the switching frequency.

And supply voltage decreases dynamic power also decreases.

Electrical Power Vs Voltage

Electric power can be defined as the energy dissipate or produced per unit of time. The measuring component of power is the watt.

The electrical power of a circuit can be described as the product of voltage (or electric potential energy) and current through the circuit. Power through a circuit can be measured by using a power meter.

Voltage can be described as the potential drop between two points. The measuring unit of voltage is Volt. Voltage can be defined as the product of Volt and charge. The voltage of a circuit can be e measured by a voltmeter.

Leakage Power Vs Voltage

Leakage power is a function of applied voltage threshold voltage and the size of the transistor. Leakage power can be reduced by lower operating voltage.

In CMOS leakage power, the power is consumed when the transistor is in the sub-threshold region, which means power consumption by the subthreshold current (current between source and drain during subthreshold of the transistor) and reverse bias diode in a CMOS transistor is known as leakage power. Leakage power can depend upon the variation of the transistor threshold voltage. Leakage power is the result of unwanted leakage current in the threshold channel when the transistor is not working.

Motor Power Vs Voltage

An electric motor is a machine that transforms or converts the electrical format of energy within the mechanical format of energy.

The power of a motor can be defined product of the rate of conservation for the generation of energy per unit time.

The relationship between power and voltage can be defined as the product of instantaneous voltage and instantaneous current is equal to instantaneous power when the motor power is constant. Still, when voltage reduces, then a current on the motor increases, and when voltage is increased, the current drawn by the motor or heat generated by the motor reduces. Still, High Voltage can saturate the magnetic component of the motor.

E-Twow Electric Motor
Image Credit : “E-Twow Electric Motor” by kasparsdambis is licensed under CC BY 2.0

When there is a phase difference between voltage and current, then the power of the motor is defined as the product of the power factor with current and voltage.

As long as the motor draw enough current from the power supply same amount of power will be generated, with different value of voltages which means with higher voltage, it doesn’t mean that the motor will generate more power.

RF Power Vs Voltage

RF power stands for radio frequency power. Radio-frequency is the high oscillation rate of AC current or voltage of any electrical, magnetic, or electromagnetic field.

A radio frequency (RF) power amplifier is a type of amplifier which transforms or modify a low-power radio frequency signal within a high-power radio frequency signal. 

Generally, an RF power amplifier is used in the transmitter’s antenna. Radio-frequency  (or RF) power or RF power is in a general sense described in dBm ( dBm is a logarithmic unit of power used in radio and microwave electronics ) with voltage for determined impedance.

In electronics, power is measured in mW and can be defined with the help of voltage drop across the impedance of the RF circuit power across RF circuit can be defined as

[latex] P = \frac{V^2}{Z} [/latex]

Where P is the power, V is the voltage, and Z is the impedance.

Reactive Power Vs Voltage

Through the power triangle, the relationship between apparent power, real power, and reactive power can be defined.

Let’s define the relationship between the reactive power and voltage. In a single-phase AC circuit with a load of Impedance Z, then instantaneous current and voltage can be defined as

[latex] v=\sqrt{2} v sin\omega t [/latex]

[latex] i = \sqrt{2} I sin(\omega t -\theta) [/latex]

where [latex] I= \frac{V}{Z} [/latex]

Now instantaneous power delivered to the load can be defined as

[latex] p=iv = 2 VI sin \omega t sin (\omega t – \theta) [/latex]

[latex] = VI [I cos \theta (1 – cos 2\omega t) + I sin \theta sin 2\omega t] [/latex]

In the above equation, the quadrature component of current I sin theta is the component of power oscillating of frequency [latex] 2\omega [/latex] to the lord with zero average value. This component of power is known as reactive power.

Reactive power can also be defined as the measure of energy exchange between the source and the reactive part of the load.

The reactive power is transferred back and forth between the source and the load, representing a lossless interchange between the source and the load; reactive power is zero for resistive load, whereas less than zero for capacitive load and more significant than zero for inductive load.

Reactive power is denoted by Q, and the unit of reactive power is volt-ampere reactive.

Generally, voltage increases with an increase in reactive power, whereas voltage decreases with a decrease in reactive power, which primary voltage is directly proportional to the reactive power, when the reactive power is constant, voltage drops which causes current to increase to maintain the power supply, which results in any system consuming more reactive power resulting in the voltage drops further.

In an AC circuit, voltage is controlled by maintaining the production and absorption of reactive power.

Sneha Panda

I have graduated in Applied Electronics and Instrumentation Engineering. I'm a curious-minded person. I have an interest and expertise in subjects like Transducer, Industrial Instrumentation, Electronics, etc. I love to learn about scientific researches and inventions, and I believe that my knowledge in this field will contribute to my future endeavors. LinkedIn ID- https://www.linkedin.com/in/sneha-panda-aa2403209/

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