Tag: thermal effect of electric current

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Multiple choice physics effects of electric current thermal effect of electric current heating effect of electric current electric current and its effects

A motor of $50\ W$ runs for $20\ hrs$. How many 'units' ($kWh$) of electrical energy are consumed?

  1. $5\ kWh$
  2. $2\ kWh$
  3. $1\ kWh$
  4. $2.5\ kWh$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Given :       $P = 0.050\ kW$ 

                   $t = 20\ h$

Energy consumed,      
$E = Pt =0.050\times 20 = 1\ kWh$

Multiple choice physics effects of electric current thermal effect of electric current heating effect of electric current electric current and its effects

Which of these will consume most units of energy in a day?

  1. A $60\ W$ bulb used for $6\ hrs$.
  2. A $30\ W$ bulb used for $12\ hrs$.
  3. A $20\ W$ bulb used for $24\ hrs$.
  4. A $100\ W$ bulb used for $2\ hrs$.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Energy consumed per day is: $E = Pt$

(A) :     $E _A = 0.06\times 6 = 0.36\ kWh$
(B) :     $E _B = 0.03\times 12 = 0.36\ kWh$ 

(C) :     $E _C = 0.02\times 24 = 0.48\ kWh$ 
(D) :     $E _D = 0.10\times 2 = 0.2\ kWh$ 

Thus bulb of option C will consume more energy.

Multiple choice physics effects of electric current thermal effect of electric current heating effect of electric current electric current and its effects

Calculate the monthly bill if a heater of 100 watt is used at the rate of rs. 1 per unit for 1 hour daily.

  1. Rs. 200

  2. Rs. 6000

  3. Rs. 100

  4. Rs. 3
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Given :       $P=0.1$ kW           $t = 1$ hour per day

Energy consumed per day     $E = Pt = 0.1\times 1 = 0.1$ kWh per day
Total energy consumed per month  $E _T = 30\times 0.1 = 3$ kWh per month
Cost of electricity  $ =Re$ $ 1 $ per unit i.e per kWh
$\therefore$  Monthly bill $ = Re.$ $1\times 3   =$Rs. $3$ per month

Multiple choice physics effects of electric current thermal effect of electric current heating effect of electric current electric current and its effects

Calculate the total power of 2 fans, if each of them draws a current of $5   A$ at a p.d of $200   V$.

  1. $2000 \omega$
  2. $1000 V$
  3. $250 \omega$
  4. $2 \omega$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$I = 5A,   p.d = 200   V$
Power $= V \times I = 200 \times 5 = 1000   \omega$
For 2 fans $= 2 \times 1000 = 2000   \omega$.

Multiple choice physics effects of electric current thermal effect of electric current heating effect of electric current electric current and its effects

Calculate the energy transferred by a $5  A$ current flowing through a resistor of $20   \ ohms$ for $30$ minutes.

  1. $25 kwh$
  2. $50 kwh$
  3. $2.5 \times {10}^{-2} kwh$
  4. $5 \times {10}^{-2} kwh$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$E = {I}^{2}Rt$
$= {5}^{2} \times 2 \times \dfrac{1}{2}$
$= 2.5 \times {10}^{-2}  kwh$