Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice physics dynamics - explaining motion system of unit summary of si units system of units

SI unit of Magnetic flux is weber and its CGS unit is maxwell. Then 1 Wb = :

  1. $10^6$ maxwell
  2. $10^7$ maxwell
  3. $10^8$ maxwell
  4. $10^9$ maxwell
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Magnetic flux is the product of magnetic field and area.

As SI unit of magnetic flux is weber, so $1 \, Wb=Tesla (T)\times m^2$
where $1 \, T=10^{4} \, gauss$ and $1 m^2=10^4 cm^2$
(T and gauss is the SI and CGS unit of magnetic field )
So, $1 \, Wb=10^4 \, gauss \times 10^4cm^2=10^8 $ maxwell

Multiple choice physics dynamics - explaining motion system of unit summary of si units system of units

$S = A(1 - e^{-Bxt})$, where S is speed and x is displacement. The unit of B is :

  1. $m^{-1}s^{-1}$
  2. $m^{-2}s$
  3. $s^{-2}$
  4. $s^{-1}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

It is given that $x$ is displacement and $t$ is time.
Unit of $x$ is $m$ and that of time t is $s$.
Since, the quantity $Bxt$ must be dimensionless.
$\implies$ Unit of B must be $m^{-1}s^{-1}$.

Multiple choice zener diode special purpose diodes electronic devices semiconductor electronics: materials, devices and simple circuits physics

Zener breakdown takes place if:

  1. Doped impurity is low

  2. Doped impurity is high

  3. Less impurity in N-part

  4. Less impurity in P-type
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

 Zener breakdown occurs due to heavily doped diodes.In this process electrons crosses the barrier from 

the valence band of the p-type  to the conduction band of the lightly filled n-type material.

Multiple choice zener diode special purpose diodes electronic devices semiconductor electronics: materials, devices and simple circuits physics

If, a Zener diode ($V _z = 5V$ and $I _z = 10 mA$) is connected in series with a resistance and 20 V is applied across the combination, then the maximum resistance one can use without spoiling zener action is

  1. 20 $k\Omega$
  2. 15 $k\Omega$
  3. 10 $k\Omega$
  4. 1.5 $k\Omega$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The total voltage is 20V and the Zener voltage is 5V, so the voltage across the series resistor is 20 - 5 = 15V. For maximum resistance, the circuit current must be at the minimum required Zener current, which is given as 10mA. Using Ohm's law, R = V / I = 15V / 10mA = 1.5 kOmega, making option D correct.

Multiple choice zener diode special purpose diodes electronic devices semiconductor electronics: materials, devices and simple circuits physics

The main cause of Zener breakdown is

  1. the base semiconductor being germanium.

  2. production of electron-hole pairs due to thermal excitation.

  3. low doping.

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

Zener breakdown occurs in heavily doped p-n junctions. The heavy doping makes the depletion layer extremely thin. So that, carriers cannot accelerate enough to cause ionization. Thus, current will increase in reverse bias only due to reverse breakdown voltage.

Multiple choice zener diode special purpose diodes electronic devices semiconductor electronics: materials, devices and simple circuits physics

The main cause of avalanche breakdown is

  1. collision by ionisation.

  2. high doping.

  3. recombination of electrons and holes.

  4. low doping.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Avalanche breakdown is caused by impact ionization of electron-hole pairs. A very little current flows under reverse bias conditions and depletion region increases. The electric field in the depletion region of a diode can be very high. Electron/holes that enter the depletion region undergo a tremendous acceleration. As these accelerated carriers collide with the atoms, they can knock electrons from their bonds, creating additional electron/hole pairs and thus additional current. As these secondary carriers are swept into the depletion region, they too are accelerated and the process repeats itself.