Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice physics measurements and units measurement of area and volume measurement of volume measurement of area, volume and density

A public park, in the form of a square, has an area of $(100 \pm 0.2 )m^2 $ .The side of park is :

  1. $ (10 \pm 0.01 ) m $
  2. $ (10 \pm 0.1 ) m $
  3. $ (10 \pm 0.02 ) m $
  4. $ (10 \pm 0.2 ) m $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let the side length of the square park is $l$.

The area of a square is given as,

$A = {l^2}$

$100 = {l^2}$

$l = 10\;{\rm{m}}$

The error in length is given as,

$\dfrac{{\Delta A}}{A} = 2\dfrac{{\Delta l}}{l}$

$\dfrac{{0.2}}{{100}} = 2\dfrac{{\Delta l}}{{10}}$

$\Delta l = 0.01\;{\rm{m}}$

Thus, the side of the park is $\left( {10 \pm 0.01} \right)\;{\rm{m}}$.

Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

The input resistance of a silicon transistor is $1 k\Omega $.If base current is changed by $100 \mu A$ it causes the change in collector current by $2 mA$. This transistor is used as a CE amplifier with a load resistance of $5 k\Omega$ What is the ac voltage gain of amplifier?

  1. $10$
  2. 44100$
  3. $500$
  4. $200$
Reveal answer Fill a bubble to check yourself
D Correct answer
Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

In a silicon transistor the base current is changed by $25\mu A$. This results in a change of $0.04\ V$ in the base to emitter voltage and a change of $4\ mA$ in the collector current. The trans-conductance of the transistor (in $\Omega^{-1}$) is

  1. $0.1$
  2. $1$
  3. $1000$
  4. $0.01$
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

For a common emitter configuration, If $\alpha $and $\beta $ have thier usual meanings. The incorrect relationship between $\alpha $and $\beta $ is:

  1. $\alpha =\dfrac { \beta }{ 1-\beta } $
  2. $\alpha =\dfrac { \beta }{ 1+\beta } $
  3. $\alpha =\dfrac { { \beta }^{ 2 } }{ 1+{ \beta }^{ 2 } } $
  4. $\dfrac { 1 }{ \alpha } =\dfrac { 1 }{ \beta } +1$
Reveal answer Fill a bubble to check yourself
B,D Correct answer
Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

For a common emitter connection the values of constant collector current and base current are $5\ mA$ and $50$$\mu A$ respectively. The current gain will be

  1. $10$
  2. $20$
  3. $40$
  4. $100$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Given that:
$I _c = 5\ mA$
$I _b = 50\ \mu A = 5 \times 10^{-2}\ mA$
The current gain is
$\beta = \dfrac{I _c}{I _b}$
$\beta = \dfrac{5}{5 \times 10^{-2}} = 100$

Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

In a silicon transistor, the base  current is changed by 20 change of 0.02V in base to emitter voltage and a change of 2mA in the collector current.
(a) Find the input  resistance ${ \beta  } _{ ac }$ 
(b) If this transistor is used as an-amplifier. Find the voltage gain of the-amplifier with the load resistance 5k amplifier.

  1. a)100b)-500

  2. a)1000b)-500

  3. a)2000b)-5000

  4. a)10b)-5
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

(a) $n=\frac { { \triangle v } _{ BE } }{ { \triangle | } _{ B } } =\frac { 0.02 }{ 20\times { 10 }^{ -6 } } =1k\Omega $
${ \beta  } _{ ac }=\frac { { \triangle | } _{ c } }{ { \triangle | } _{ B } } =\frac { 2\times { 10 }^{ -3 } }{ 20\times { 10 }^{ -6 } } =100$
(b) Voltage gain,${ A } _{ v }=-{ g } _{ m }{ R } _{ L }=-\left( 0.1 \right) \left( 5\times { 10 }^{ 3 } \right) =-500$. $\left( since\quad { g } _{ m }={ \beta  } _{ ac }/n \right) $

Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

The ac current gain of a transistor is $120$. What is the change in the collector current in the transistor whose base current changes by $100\ \mu A$?

  1. $6\ mA$
  2. $12\ mA$
  3. $3\ mA$
  4. $24\ mA$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given that,

Current gain$\beta =120\,A$

Base current $\Delta {{I} _{b}}=100\,\mu A$


We know that,

  $ {{\beta } _{ac}}=\dfrac{\Delta {{I} _{C}}}{\Delta {{I} _{B}}} $

 $ \Delta {{I} _{C}}=120\times 100\times {{10}^{-6}} $

 $ \Delta {{I} _{C}}=12\times {{10}^{-3}}\,A $

 $ \Delta {{I} _{C}}=12\,mA $

Hence, the collector current in the transistor is $12\ mA$