Tag: electric current and its effects

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Questions Related to electric current and its effects

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

The essential requirements for a good heating element are _________________.

  1. High resistivity and low melting point

  2. High resistivity and high melting point

  3. Low resistivity and low melting point

  4. Low resistivity and high melting point
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

ESSENTIAL REQUIREMENTS OF GOOD HEATING ELEMENT High-specific resistance so that small length of wire may be required to provide given amount of heat. High-melting point so that it can withstand for high temperature, a small increase in temperature will not destroy the element.

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

If the current is flowing through a $10 \Omega$ resistor, then in which case the maximum heat will be generated?

  1. $5 \ ampere \ in \ 2 \ minutes$
  2. $4 \ ampere \ in \ 3 \ minutes$
  3. $3 \ ampere \ in \ 6\ minutes$
  4. $2 \ ampere \ in \ 5 \ minutes$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Heat generated $H = i^2 Rt$

(A) : $H _A = (5)^2 (10) (2\times 60) = 30 kJ$
(B) : $H _B = (4)^2 (10) (3\times 60) = 28.8 kJ$

(C) : $H _C = (3)^2 (10) (6\times 60) = 32.4 kJ$
(D) : $H _D = (2)^2 (10) (5\times 60) = 12 kJ$

Thus maximum heat is generated in case $C$.

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

Name the effect of current responsible for the glow of the bulb in an electric circuit.

  1. Chemical

  2. Heating

  3. Magnetic

  4. Heating and Magnetic
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The electric bulb has a filament called tungsten when electricity passes through this filament, it heats up and glows. 

This heat is generated due to the passage of electric current, the drift of electrons due to the current and the resistance it has.
Hence, the heating effect of electric current is responsible for the glow of the bulb in an electric circuit.

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

A house is fitted with 10 tubes of 40 W. If all tubes are lighted for 10 hours and if the cost of one unit of electricity energy is Rs. 2.50 the total cost of electricity consumption is ...

  1. Rs. $100$
  2. Rs. $20$
  3. Rs. $25$
  4. Rs. $10$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Total power = 10 tubes * 40 W = 400 W = 0.4 kW. Energy = 0.4 kW * 10 hours = 4 kWh. Cost = 4 kWh * 2.50 Rs/kWh = 10 Rs.

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

The resistance of a hot tungsten filament is about $10$ times the cold resistance. What will be the resistance of $100\ W,\ $$200\ V$ lamp when not in use?

  1. $20\Omega$
  2. $40\Omega$
  3. $200 \Omega$
  4. $400 \Omega$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
When the lamp is in use, it is hot.

Using Joule's Law of heating,
$P = \cfrac{V^2}{R}$
$R= \cfrac{200^2}{100}=400\Omega$ when operating 

It is given resistance of hot lamp is 10 times the cold lamp.
Hence, $R _{cold}=\cfrac{400}{10}=40\Omega$
Multiple choice physics electric current thermal effect of electric current heating effect of electric current electric current and its effects

You have the following appliances each of $500\ W$ running on  $220\ V$ a.c.: 

(1) Electric iron.
(2) Electric lamp. 
(3) Electric room heater. 
The electric resistance is:

  1. maximum for the heater.

  2. maximum for the electric lamp.

  3. maximum for the electric iron.

  4. same in all the three cases.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Resistance$,\ R= \dfrac{V^2}{P} =\dfrac{(220)^2}{P}$. Since $P$ of each appliance is the same, hence $R$ is same for all the three appliances.

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

An electric lamp is marked $60\ W,\ 220\ V$. The cost of kilo watt hour of electricity is $Rs.\ 1.25$. The cost of using thing lamp on $220\ V$ for $8\ hrs$ is:

  1. $Rs.\ 0.25$
  2. $Rs.\ 0.60$
  3. $Rs.\ 1.2$
  4. $Rs.\ 4.00$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given:

Power, $P=60\ W$
Time, $t=8\ hrs$

Energy consumed per day, $E=Pt=60\times 8=480\ Whr=\dfrac{480}{1000}=0.48\ kW hr$
Hence total cost, $C=0.48\times 1.25=Rs. 0.60 $

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

An electric bulb of $60\ W$ is used for $6\ hrs/day$. Calculate the units of energy consumed in one day by the bulb.

  1. $0.18\ \text{units}$
  2. $0.36\ \text{units}$
  3. $0.54\ \text{units}$
  4. $0.72\ \text{units}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given :    $t = 6\ hrs$             

                $P = 0.06\ kW$
Thus energy consumed per day is:

$E=  Pt = 0.06\times 6  = 0.36\ kWh$$ = 0.36\ \text{units}$