Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice physics force and types of force introduction to force what is force? concept of force and its unit

State whether true or False 
10 mN is equal to $10^{-3}$ dynes.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Newton (N) is a SI unit of Force while dyne is a CGS unit of force.   


Relation between them is given as 


$1 dyne=1*10^{-3}*1*10^{-2}N$
$1 dyne =10^{-5}N$
$1 N = 10^5 dyne$
$10 \ mN = 10 \times 10^{-3} N= 10^{-2} N = 10^{-2} \times 10^{5} dyne$
$10 \ mN=10^{3}dyne$

Multiple choice physics force and types of force introduction to force what is force? concept of force and its unit

Which of the following laws represents the qualitative measure of force?

  1. Newton's first law of motion

  2. Fleming's right hand rule

  3. Fleming's left hand rule

  4. Zeroth law of thermodynamics
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Newton's first law of motion represents the qualitative measure of force.It states that:

An object remains in the state of rest or of uniform motion in a straight line unless compelled to change that state by an applied unbalanced force.
All objects resist change in their state of motion. The tendency of undisturbed objects to stay at rest or to keep moving with the same velocity is called inertia. This is why, the first law of motion is also known as the law of inertia.

Multiple choice introduction to induction electromagnetic induction electromagnetic induction and alternating currents physics

A solenoid coil is wound on a frame of rectangular cross section. If all the linear dimension of the frame are increased by a factor of two and the number of turns per unit length of the coil remains the same, the self-inductance increases by a factor of

  1. $4$
  2. $8$
  3. $12$
  4. $16$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Self inductance, $L = \dfrac{\mu 0 N^2 A}{l}$ _(1)


where N = total number of turns


$n = \dfrac{N}{l}$, where n = number of turns per unit length

$N = nl$ put it in (1)

$L = \dfrac{\mu _0 (n l )^2 A}{l} = \mu _0 n^2 l A$

In the given question n is same
Area will increase by $4$ times
length will increase by $2$ times

$L' = \mu _0 n^2 (2l) (4A) = 8 \mu _0 n^2 lA$

$L' = 8L$ inductance will increased by $8$ times.

Multiple choice introduction to induction electromagnetic induction electromagnetic induction and alternating currents physics

The unit of inductance is equivalent to

  1. $\dfrac {volt\times ampere}{second}$
  2. $\dfrac { ampere}{volt\times second}$
  3. $\dfrac {volt}{Ampere\times second}$
  4. $\dfrac {volt\times second}{ampere}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$As \, \varepsilon \, = \,  L \, \dfrac{dI}{dt},$
$L \, = \, \varepsilon \dfrac{dt}{dI} \Rightarrow \, L \, = \, \dfrac{volt \times second}{ampere}$

Multiple choice introduction to induction electromagnetic induction electromagnetic induction and alternating currents physics

Two concentric co-planar circular loops of radii $r _1$ and $r _2$ carry currents of respectively $i _1$ and $i _2$ in opposite directions (one clockwise and the other anticlockwise.) The magnetic induction at the centre of loops is half that due to $i _1$ alone at the centre. If $r _2 = 2r _1$. the value of $i _2 / i _1$ is 

  1. $2$
  2. $\dfrac{1}{2}$
  3. $\dfrac{1}{4}$
  4. $1$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$\begin{array}{l} B=\frac { { { \mu _{ o } }{ i _{ 1 } } } }{ { 2{ r _{ 1 } } } } -\frac { { { \mu _{ o } }{ i _{ 2 } } } }{ { 2\left( { 2{ r _{ 1 } } } \right)  } }  \ =\frac { { { \mu _{ o } }{ i _{ 1 } } } }{ { 2{ r _{ 1 } } } } -\frac { { { \mu _{ o } }{ i _{ 2 } } } }{ { 4{ r _{ 2 } } } }  \ { B^{ ' } }=\frac { { { \mu _{ o } }{ i _{ 1 } } } }{ { 2{ r _{ 1 } } } }  \ \Rightarrow B=\frac { { { B^{ ' } } } }{ 2 }  \ \Rightarrow \frac { { { \mu _{ o } }{ i _{ 1 } } } }{ { 2{ r _{ 1 } } } } -\frac { { { \mu _{ o } }{ i _{ 2 } } } }{ { 4{ r _{ 1 } } } } =\frac { { { \mu _{ o } }{ i _{ 1 } } } }{ { 4{ r _{ 1 } } } }  \ \Rightarrow \frac { { { \mu _{ o } }{ i _{ 1 } } } }{ { 4{ r _{ 1 } } } } =\frac { { { \mu _{ o } }{ i _{ 2 } } } }{ { 4{ r _{ 1 } } } }  \ \Rightarrow \frac { { { i _{ 1 } } } }{ { { i _{ 2 } } } } =1 \ Hence, \ option\, \, D\, \, is\, \, correct\, \, answer. \end{array}$

Multiple choice introduction to induction electromagnetic induction electromagnetic induction and alternating currents physics

When the number of turns in a solenoid is doubled without any change in the length of the solenoid, its self-inductance becomes :

  1. Half

  2. Double

  3. Four times

  4. Eight times
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Self-inductance,
$\begin{array}{l}L \propto {N^2}\\therefore \dfrac{{{L _1}}}{{{L _2}}} = {\left( {\dfrac{{{N _1}}}{{{N _2}}}} \right)^2} = {(2)^2} = 4...........{ since,{N _2} = 2{N _1}} \\left[ {{L _2} = 4{L _1}} \right]\end{array}$

Multiple choice introduction to induction electromagnetic induction electromagnetic induction and alternating currents physics

Which of the following does not have the same dimensions as the Henry?

  1. $\dfrac{\text {joule}}{(\text{ampere})^2}$
  2. $\dfrac{\text {tesla} - m^2}{(\text{ampere})^2}$
  3. $\text{ohm-second}$
  4. $\dfrac{1}{\text{Farad-second}}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Option $D$ is does not have the same dimensions as the Henry.

So, Option $D$ is correct.