Explanation

A dipole in an electric field behaves in two ways:

• In a uniform electric field:

The two equal and opposite forces cancel each other out.

So, the net force on the dipole is zero.

But a torque is produced that tends to align the dipole moment parallel to the electric field.

• In a non-uniform electric field:

The dipole does experience a net force, and that force is generally not simply parallel to the field.

So the correct answer remains:

(D) None of these — because in a uniform electric field, the net force on a dipole is zero.

Option (C) would be correct only if we were talking about torque direction or net force in a non-uniform field.

Explanation

 Lenz's law is a consequence of the law of conservation of energy. 

Lenz's law states that the induced current in a conductor always opposes the change in magnetic flux that caused it, which is essentially a way of ensuring that energy is conserved. 

Explanation

Silicon is the most widely used material in semiconductor devices due to its:

• Abundance in nature

• Suitable electrical properties

• Excellent thermal stability

• Formation of a stable oxide layer (SiO₂), which is useful in device fabrication

While germanium was used in early semiconductors and gallium nitride is used in high-power or high-frequency applications, silicon remains the industry standard.

Explanation

 The temperature coefficient of resistance indicates how the resistance of a material changes with temperature.

In semiconductors, as temperature increases, more charge carriers (electrons and holes) become available, so resistance decreases.

Therefore, the temperature coefficient is negative.

Explanation

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

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

As a raindrop falls:

• Initially, it accelerates due to gravity.

• As its speed increases, air resistance (a drag force) also increases.

• Eventually, a point is reached where the upward air resistance equals the downward gravitational force.

• At this point, net force = 0, so acceleration stops, and the raindrop continues falling at a constant speed.

This constant speed is called terminal velocity.

Explanation

The unit of magnetic flux density is Wb m⁻² (weber per square meter).

It is commonly referred to as a tesla (T), which quantifies the strength of the magnetic field.

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

Ferromagnetic materials (such as iron, cobalt, and nickel) have a strong attraction to magnetic fields and can retain their magnetism even after the external magnetic field is removed.

This property makes them ideal for making permanent magnets.

• Diamagnetic materials are repelled by magnetic fields and cannot retain magnetism.

• Paramagnetic materials are weakly attracted to magnetic fields but do not retain magnetism after the external field is removed.

Explanation

Lasers operate on the principle of stimulated emission, proposed by Einstein.

In stimulated emission, an incoming photon stimulates an excited atom to drop to a lower energy level, releasing a new photon.

This new photon has:

• Same energy
• Same wavelength
• Same polarization
• Same phase and direction
• as the photon that stimulated it.

Because of this process, all photons in a laser beam are coherent, monochromatic, and travel in the same direction — a unique property of laser light.