# How do you find average power density?

## How do you find average power density?

How to calculate power density easily – Even in your head!

- Convert the diameter to cm,
- Divide the diameter by two to find the radius,
- Use πr^2 to find the area in cm^
- And, finally, divide the laser power by the area to obtain power density.

**What is average power density?**

Let’s start with a definition: power density is power per unit area which is usually expressed in terms of W/cm^2. The Calculation of power density is pretty simple – composed of 2 steps: Calculate the area of a beam using the radius in cm. Divide the beam’s power by that area.

### How do you calculate the average power of a wave?

The time-averaged power of a sinusoidal wave on a string is found by Pave=12μA2ω2v, P ave = 1 2 μ A 2 ω 2 v , where μ is the linear mass density of the string, A is the amplitude of the wave, ω is the angular frequency of the wave, and v is the speed of the wave.

**What is the time average Poynting vector for an electromagnetic wave propagating in free space SI unit?**

If an electromagnetic wave falls onto an area A where it is absorbed, then the power delivered to that area is P = S∙A. The time average of the magnitude of the Poynting vector, , is called the irradiance or intensity. The irradiance is the average energy per unit area per unit time. = /(μ0c) = Emax2/(2μ0c).

#### How do you calculate LPD?

To complete the calculation, the total allowed power is first determined by multiplying the total building area by the maximum allowed power density. Next, the total lighting power of all installed fixtures is calculated. Finally, the installed power is compared to the allowed power, and must be less to meet Code.

**How do you find the average power of a sine wave?**

The average value of a sine wave of voltage or current is 0.637 times the peak value, (Vp or Ip. This mathematical relationship between the average values applies to both AC current and AC voltage.

## What is the average power transmitted along the string?

Hence Correct answer is 1.6watt.

**What is the expression for Poynting vector in free space?**

The Poynting vector S is defined as to be equal to the cross product (1/μ)E × B, where μ is the permeability of the medium through which the radiation passes (see magnetic permeability), E is the electric field, and B is the magnetic field.

### What is expression for the Poynting vector in free space?

d) S = E X B/2μo. Explanation: Poynting vector can be defined as the rate at which the energy is carried out of the volume across the bounding surface. It is always in the direction of the propagation of wave, as it is perpendicular to both electric and magnetic field.

**What is LPD value?**

Lighting power density is a simple screening measure that indicates whether a space offers opportunities for energy savings. Lighting Power Density (LPD) is defined as watts of lighting per square foot of room floor area (W/sf).