Home » Posts tagged 'Power'

# Tag Archives: Power

## Wave particle duality

Let n and m denote the number of photons emitted by a red and blue bulb respectively of equal power in a given time.Is n=m?

Answer:

No

The energy of a photon is hν

where ν is the frequency.

Power = energy/time

==> nhν1 = mhν2

==> nν1 = mν2

clearly** n not equal to m**

## Power Factor

Divya asked:

“A COIL HAS A POWER FACTOR OF 0.707 AT 60Hz, THEN ITS POWER FACTOR AT 180Hz WILL BE- ……….?

Ans:

(to be posted soon)

## A Problem from power

Gayathri Shinde Asks:

“Please answer this question with explanation:

The power output of a machine that lifts a 600 kg

weight through a height of 20m in 1min is:

@)1.96kW b)0.98kWc)12kW d)3.92kW”

Answer:

Use the formula power = work /time

[youtube=http://www.youtube.com/watch?v=BVxEEn3w688&rel=0&w=480&h=390]

## Power factor in AC circuits

Dany Asked:

“what is meant by power factor?”

Ans:

In AC circuits, Power factor is defined as the ratio of true power to apparent power.

If φ is the phase difference between E and I, then

True Power = E_{v}I_{v} cos φ and the Apparent Power is E_{v}I_{v}

Therefore,