Tag: electric current and its effects

Questions Related to electric current and its effects

The essential requirements for a good heating element are _________________.

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

  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

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Correct Option: D
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.

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

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

  1. $5 \ ampere \ in \ 2 \ minutes$

  2. $4 \ ampere \ in \ 3 \ minutes$

  3. $3 \ ampere \ in \ 6\ minutes$

  4. $2 \ ampere \ in \ 5 \ minutes$

Show answer
Correct Option: C
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 $C$.

What is CFL ?

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

  1. Compact Fluorescent Lamp

  2. Compact Fluorescent Lamina

  3. Complete Fluorescent Light

  4. Controlled Fluorescent Light

Show answer
Correct Option: A
Explanation:

CFL is Compact Fluorescent Lamp.


It is widely used now days because of low pollution and low power consumption.
Answer-(A)

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

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

  1. Chemical

  2. Heating

  3. Magnetic

  4. Heating and Magnetic

Show answer
Correct Option: B
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.

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 ...

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

  1. Rs. $100$

  2. Rs. $20$

  3. Rs. $25$

  4. Rs. $10$

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Correct Option: D

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?

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

  1. $20\Omega$

  2. $40\Omega$

  3. $200 \Omega$

  4. $400 \Omega$

Show answer
Correct Option: B
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, $R _{cold}=\cfrac{400}{10}=40\Omega$

Calculate the energy consumed by $2\ kW$ heater used for $1\ hr$ every day in a period of $30\ \text{days}$.

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

  1. $60\ \text{units}$

  2. $120\ \text{units}$

  3. $15\ \text{units}$

  4. $30\ \text{units}$

Show answer
Correct Option: A
Explanation:

$E= Pt = 2 kW\times (30 \times 1 hr)=60 kW h=60\ \text{units}$

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:

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

  1. maximum for the heater.

  2. maximum for the electric lamp.

  3. maximum for the electric iron.

  4. same in all the three cases.

Show answer
Correct Option: D
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.

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:

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

  1. $Rs.\ 0.25$

  2. $Rs.\ 0.60$

  3. $Rs.\ 1.2$

  4. $Rs.\ 4.00$

Show answer
Correct Option: B
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 $

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

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

  1. $0.18\ \text{units}$

  2. $0.36\ \text{units}$

  3. $0.54\ \text{units}$

  4. $0.72\ \text{units}$

Show answer
Correct Option: B
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}$