Explanation

• In semiconductors, as the temperature increases, the conductivity increases.
• This is because heat energy excites more electrons into the conduction band, allowing them to flow more freely and increasing the conductivity.
• This is in contrast to metals, where conductivity typically decreases with increasing temperature.

Explanation

• The resistance of a filament lamp increases at higher voltages.
• The increase in voltage leads to an increase in current, which heats up the filament and increases the resistance.
• The increased temperature causes the atoms in the filament to vibrate more, making it more difficult for electrons to pass through and increasing the resistance.

Explanation

At constant temperature, the resistance (R) of a conductor is inversely related to its cross-sectional area (A). This is expressed by the formula: R = ρ × L / A

where:

• R is the resistance
• ρ (rho) is the resistivity of the material
• L is the length of the conductor
• A is the cross-sectional area

As the cross-sectional area (A) increases, the resistance (R) decreases, and vice versa. This is why thicker wires have lower resistance than thinner wires.

Explanation

• A microphone converts sound waves into electrical signals, which are analogue in nature.
• The voltage signal generated by a microphone is a continuous signal that varies in amplitude and frequency in response to the sound waves.
• This signal is an analogue representation of the sound wave, and it is not digital.

Explanation

• A periscope requires a prism that can reflect light by 90 degrees, allowing the user to see around obstacles or over walls.
• An isosceles right-angled prism, also known as a 45-degree prism, is ideal for this purpose.
• It has two equal sides and a 90-degree angle between them, which allows for total internal reflection and a clear image.

Explanation

AM (Amplitude Modulation) radio operates in the frequency range of 550 to 1700 KHz.

Explanation

The type of gas utilized in refrigerators to chill water is Tetrafluoroethane, also known as R-134a or HFC-134a.

Explanation

Explanation

• Substances with permeability less than that of free space (μ₀) are called diamagnetic materials.
• These materials are weakly repelled by magnetic fields and have a relative permeability (μr) less than 1.

Explanation

• The main constituent of Permalloy is nickel-iron.
• Permalloy is a nickel-iron magnetic alloy, with about 80% nickel and 20% iron content, and is used as a magnetic core material in electrical and electronic equipment, as well as in magnetic shielding to block magnetic fields.