2024 - JAMB Physics Past Questions and Answers - page 5

The energy gap band refers to the energy difference between the valence band and the conduction band in a solid material.

• Insulators: Have a very large energy gap, requiring a large amount of energy to excite an electron from the valence band to the conduction band, making it difficult for electrons to move freely and conduct electricity.
• Conductors: Have a very small or no energy gap (bands overlap), allowing electrons to move freely and conduct electricity well.
• Semiconductors: Have an intermediate energy gap, with conductivity between that of conductors and insulators.
• Intrinsic semiconductors: Pure semiconductors whose conductivity depends on temperature.

Therefore, the material with the largest energy gap band is an insulator.

The upthrust is calculated using Archimedes' principle: Upthrust = ρ V g, where:

• ρ is the density of the liquid (1028 kg/m³)
• V is the volume of the ball (4.2 x 10^-4 m³)
• g is the acceleration due to gravity (≈ 9.8 m/s²)

Calculate the upthrust:

Upthrust = 1028 * 4.2 x 10^-4 * 9.8 ≈ 4.22 N

The closest option to the calculated upthrust is 4.3 N.

The beat frequency is the difference between the frequencies of the two sound waves.

Beat frequency = 6 Hz - 4 Hz = 2 Hz

Convert units: 500 cm = 5 m.

Calculate work done: W = F * d = 50 * 5 = 250 J

Calculate power: P = W / t = 250 / 1 = 250 W

The relationship between charge (Q), voltage (V), and capacitance (C) is Q = C V. Solve for capacitance: C = Q / V

Given Q = 30 C and V = 5 V,

C = 30 / 5 = 6 F

In a series resonant circuit, the impedance is at its minimum value. Since current I = V / Z, the current is maximum when impedance is minimum.

The process of adding impurities to a semiconductor material to increase its conductivity is called doping.

• Doping: Deliberate introduction of impurities into a semiconductor to increase the number of charge carriers, thereby increasing conductivity.
• Rectification: Converting alternating current (AC) to direct current (DC).
• Emission: Release of electrons from a material.
• Stabilization: Making something stable or preventing it from changing.

Given thermal capacity C = 400 J/K, temperature change ΔT = 80ºC - 60ºC = 20 K.

Quantity of heat: Q = C * ΔT = 400 * 20 = 8000 J = 8 kJ

Using the mirror formula: 1/f = 1/v + 1/u

Given: u = -25 cm (object distance, negative for mirrors), v = 5 cm (image distance, positive for convex mirrors)

Plug in values: 1/f = 1/5 + 1/(-25) = 0.2 - 0.04 = 0.16

Thus, f = 1 / 0.16 ≈ 6.25 cm

A voltameter is designed to measure the quantity of electricity passed through a solution during electrolysis by determining the amount of substance deposited or liberated at the electrodes. While an ammeter measures current and a voltmeter measures voltage, they do not directly allow investigation of electrolysis like a voltameter. A galvanometer detects small currents.