Tag: thermal effect of electric current

Questions Related to thermal effect of electric current

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

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

  1. $5\ kWh$

  2. $2\ kWh$

  3. $1\ kWh$

  4. $2.5\ kWh$

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Correct Option: C
Explanation:

Given :       $P = 0.050\ kW$ 

                   $t = 20\ h$

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

A heater is marked 1000 W. The energy consumed by it in ten hours is

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

  1. 10 J

  2. 10 KJ

  3. 10 kWh

  4. 100 KJ

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Correct Option: C
Explanation:

Given :    $P = 1000$ W $=1$ kW              $t = 10$ h

$\therefore$ Energy consumed in 10 h       $E = Pt = 1\times 10 =10$ kWh

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

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

  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 $2\ hrs$.

Show answer
Correct Option: C
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.

A current of $4  A$ flows through a $12  V$ car headlight bulb for $10$ minutes, how much energy is consumed?

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

  1. $8 \times {10}^{-3} kwh$

  2. $48 kwh$

  3. $8 kwh$

  4. $8 \times {10}^{3} kwh$

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Correct Option: A
Explanation:

$E = VIt$
  $= 12 \times 4 \times \dfrac{1}{6}$
  $= 8 \times {10}^{-3}   kwh$

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

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

  1. Rs. 200

  2. Rs. 6000

  3. Rs. 100

  4. Rs. 3

Show answer
Correct Option: D
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

What should be the bill for the month of March for a heater of resistance $\displaystyle $ connector to 220V mains. The cost of energy is Rs.1 kWh and the heater is used 1 hour daily.

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

  1. Rs. 144

  2. Rs. 60

  3. Rs. 72

  4. Rs. 50

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Correct Option: C

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

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

  1. $2000 \omega$

  2. $1000 V$

  3. $250 \omega$

  4. $2 \omega$

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Correct Option: A
Explanation:

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

A current of $0.5  A$ flows through a resistance of $10  \Omega$ for $\dfrac{1}{2}$ hour. Find the amount of electrical energy consumed by resistance.

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

  1. $450 J$

  2. $4500 J$

  3. $45 J$

  4. $45000 J$

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Correct Option: B
Explanation:

$E = {I}^{2}RT = {0.5}^{2} \times 10 \times 1800$
       $= 4500  J$

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

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

  1. $25 kwh$

  2. $50 kwh$

  3. $2.5 \times {10}^{-2} kwh$

  4. $5 \times {10}^{-2} kwh$

Show answer
Correct Option: C
Explanation:

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

An electric bulb is rated $750   \omega - 200   V$. Calculate the magnitude of current.

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

  1. $200 A$

  2. $3.75 A$

  3. $15 A$

  4. $2 A$

Show answer
Correct Option: B
Explanation:

$V = 200   V,   P = 750   \omega$.
$P = VI ,   750 = 200 \times I$
$I = 3.75   A$.