Explanation

• Faraday’s 1821 experiment was the first electric motor demonstration.
• A wire carrying current was made to rotate around a magnet.
• This proved that electricity can produce mechanical motion.
• It laid the foundation for electromagnetic machines and motors.

Last updated on 09-03-2026

Explanation

Silicon is widely used in semiconductors because:

• It is abundant in nature.
• It has suitable electrical properties.
• It has excellent thermal stability.
• It forms a stable oxide layer (SiO₂) useful in device fabrication.

Note: Germanium was used earlier, and gallium nitride is used for high-power or high-frequency devices, but silicon remains the standard.

Last updated 14-feb-2026

Explanation

 When a forward bias is applied to a p-n junction:

The potential barrier decreases.

Electrons from the n-side move toward the p-side.

These electrons are minority carriers on the p-side.

As a result, the concentration of electrons on the p-side increases, but only slightly, since it's still a small number compared to the holes (which are majority carriers on the p-side).

Explanation

If an electron has zero orbital angular momentum, its magnetic dipole moment also equals zero

This is because the magnetic dipole moment is directly proportional to the orbital angular momentum, and when the angular momentum is zero, the magnetic moment is also zero. 

Explanation

In an intrinsic semiconductor, there are equal numbers of electrons in the conduction band and holes in the valence band

So the Fermi level, which represents the energy level at which the probability of finding an electron is 50%

Lies right in the middle of the band gap between the valence and conduction bands. 

Explanation

The stopping potential is the voltage applied to the electrodes in a photoelectric effect experiment that just prevents the most energetic electrons from reaching the anode.

Since the kinetic energy of the ejected electrons is directly proportional to the frequency of the incident light (above the threshold frequency), a higher frequency light will result in more energetic electrons.

Therefore, the stopping potential, which is the voltage needed to completely stop these most energetic electrons, is also directly proportional to their energy. 

Explanation

Resistivity is a measure of how strongly a material opposes the flow of electric current.

Here's a general classification based on resistivity (in Ω-cm):

$10^5$ and 10 ^9 Ω-cm, it is classified as an insulator because it resists the flow of electric current very strongly.

Explanation

To find which body has the largest kinetic energy, we use the formula for kinetic energy:

$$text{K.E.} = frac{1}{2}mv^2$$

Mass = 2M, Speed = 3V

$$$$K.E.d=12⋅2M⋅(3V)2

$$$$
=12⋅2M⋅9V2

$$text{K.E.}_d = frac{1}{2} cdot 2M cdot (3V)^2 = frac{1}{2} cdot 2M cdot 9V^2 = 9MV^2$$K.E.d​=1​/2⋅2M⋅(3V)^2=1/2​⋅2M⋅9V^2=9MV^2

Explanation

In a pure (intrinsic) semiconductor:

• The number of electrons in the conduction band is equal to the number of holes in the valence band.

• As a result, the Fermi level lies midway between the conduction band and the valence band.

• This midpoint represents the energy level at which the probability of finding an electron is 50% at absolute zero.

This is a key difference from doped (extrinsic) semiconductors, where the Fermi level shifts depending on the type of doping (n-type or p-type).

Explanation

The energy gap (also called band gap) is the energy difference between the valence band (where electrons are bound) and the conduction band (where electrons are free to move).

• In conductors, the band gap is zero or overlaps.

• In semiconductors, the band gap is around 1 eV (e.g., silicon ≈ 1.1 eV).

• In insulators: The band gap is large, typically greater than 3 eV, and often around 5 eV or more.

This large gap in insulators prevents electrons from moving to the conduction band, making them poor conductors of electricity