Explanation

Present perfect tense ("have + past participle") requires known.

Correct sentence → I have known him for 3 years.

Explanation

"Laid" means put/placed something, but here the subject is resting.

The correct verb is "lay" → He lay there for some time.

Explanation

Transistors act as switches and amplifiers, making them essential in audio/video recorders, TVs, computers, and radios.

They are the building blocks of modern electronic circuits.

Explanation

The uranium isotope used in nuclear reactions is 92 U-235. 

Uranium-235 is a fissile isotope, meaning it can undergo nuclear fission when struck by a neutron,

Releasing energy and more neutrons to sustain a chain reaction.

While Uranium-238 is the most abundant isotope of uranium,

It is not fissile and requires a more complex process to be utilized in nuclear reactions. 

Explanation

Internal combustion engines generally use liquid fuels (like petrol, diesel) or gaseous fuels (like CNG, LPG).

Solid fuels are not suitable because they cannot be efficiently injected and combusted inside the engine cylinder.

Explanation

Specific heat capacity is the amount of heat required to raise the temperature of 1 unit mass of a substance by 1°C (or 1 K).

Hence, it is defined per unit mass of the material.

Explanation

Real gases show deviation from ideal behavior at low temperature and high pressure.

Due to increased intermolecular forces and reduced volume available for gas molecules, which contradicts the assumptions of ideal gas behavior.

Explanation

Humidity is the measure of the concentration of water vapor in the atmosphere.

Dew, mist, and fog are results of condensation, not the amount of vapor itself.

Explanation

An ammeter is an instrument used to measure small electric current in a circuit.

It typically measures current in amperes (A).

It is connected in series with the circuit.

The potentiometer is used to measure emf.

A meter bridge is used to measure the electrical resistance.

Explanation

When iron is magnetized, the alignment of magnetic domains causes a slight increase in length (called magnetostriction).

The change is very small but measurable.