Tag: electric current

Quizzes (8) Questions (16)

Questions Related to electric current

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. <span>$Rs.\ 0.60$</span>

  3. <span>$Rs.\ 1.2$</span>

  4. <span>$Rs.\ 4.00$</span>
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. <span>$0.36\ \text{units}$</span>

  3. <span>$0.54\ \text{units}$</span>

  4. <span>$0.72\ \text{units}$</span>
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}$

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

An electric bulb of $30\ W$ consumes $0.72$ units of energy in a day. Find the number of hours it is working in a day?

  1. $6\ hrs$

  2. $12\ hrs$

  3. $18\ hrs$

  4. $24\ hrs$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Given :   $P =0.030$ kW
Energy consumed per day       $E= 0.72\ \text{units}$$ = 0.72\ kWh$
Using   $E = P\times t$
$\therefore$   $0.72 = 0.03\times t$               
$\implies t = 24\ hrs$
Multiple choice physics electric current drift velocity and mobility drift speed drift velocity & mobility

A current I flows through a uniform wire of diameter d when the mean electron drift velocity is
V. The same current will flow through a wire of diameter d/2 made of the same material if the
mean drift velocity of the electron is:

  1. v/4

  2. v/2

  3. 2v

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

Let I be the current flow through wire. 

Let V be the drift velocity of wire which has diameter d. 
Let A be the area of wire. 
Consider a wire of same material but diameter is half
Therefore, Area =$\dfrac{A}{4}$
Since, $I=NeAV$
N is same for both wire because both of them made of same material. 
$I _{1}=I _{2}$
$NeA _{1}V _{1}=NeA _{2}V _{2}$
$AV=\dfrac{A}{4}V _2$
$V _{2}=4V$