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Multiple choice physics work and energy commercial unit of energy power work and power

Smallest commercial unit of energy is

  1. Kilowatt hour

  2. Watt second

  3. Watt hour

  4. Watt minutes
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Smallest commercial unit of energy is called Watt hour. It is defined as the amount of electric energy, which flows through a conductor in one hour, at a power of one watt.

Multiple choice physics work and energy commercial unit of energy power work and power

Biggest commercial unit of energy.

  1. $kwh$
  2. $BOT$
  3. $kVAh$

  4. All
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The biggest commercial unit of energy is kilowatt hour $\left(kwh\right)$. It is also known as kilo-volt-ampere hour $\left(kVAh\right)$ and board of trade unit (BOT) or simply electric unit.

Multiple choice physics work and energy commercial unit of energy power work and power

A lamp rated 20w and an electric iron rated 50w are used for 2 hour everyday. Calculate the total energy consumed in 20 days.

  1. 14kwh

  2. 2.8kwh

  3. 40kwh

  4. All
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Energy consumed by lamp in 2 hour     $E _l = 0.02\times 2 = 0.04$ kWh per day

Energy consumed by iron in 2 hour     $E _i = 0.05\times 2 = 0.1$ kWh per day
$\therefore$ Total energy consumed by both appliance     $E _T = (E _l+E _i)\times 20 = (0.04+0.1)\times 20 = 2.8$ kWh

Multiple choice physics work and energy commercial unit of energy power work and power

One kilowatt hour is equal to

  1. $\displaystyle 36\times { 10 }^{ 5 }$ joules
  2. $\displaystyle 36\times { 10 }^{ 3 }$ joules
  3. $\displaystyle { 10 }^{ 3 }$ joules
  4. $\displaystyle { 10 }^{ 5 }$ joules
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$1$ kW  $ = 1000$ $\dfrac{J}{s}$            

$1$ h $ = 3600$ s
$\therefore$  $1$ kWh $ = 1000\dfrac{J}{s}\times 3600$ $s  =36\times 10^5$  $J$

Multiple choice physics work and energy commercial unit of energy power work and power

Number of KWh in 1Joule.

  1. $\displaystyle 3.6\times { 10 }^{ 6 }KWh$
  2. $\displaystyle 2.77\times { 10 }^{ -7 }KWh$
  3. $\displaystyle 600KWh$
  4. $\displaystyle 1.6\times { 10 }^{ -19 }KWh$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

We know  $1$ kWh $ = 3.6\times 10^6$ $J$

$\therefore$  $1$ $J = \dfrac{1}{3.6\times 10^6} = 2.77\times 10^{-7}$ kWh

Multiple choice physics work and energy commercial unit of energy power work and power

Calculate the number of Joules in 1KWh.

  1. $\displaystyle 6\times { 10 }^{ -19 }J$
  2. $\displaystyle 3.6\times { 10 }^{ 6 }J$
  3. $\displaystyle 60J$
  4. $\displaystyle 59J$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$1$ kW $ = 1000$ $\dfrac{J}{s}$

$1$ h $=3600$ s 
$\therefore$  $1$ kWh $ = 1000\dfrac{J}{s}\times 3600$ $s  =3.6\times 10^6$  $J$