Physics 2024 Jamb Examination

Since 20% of the hydrometer is above the fluid, 80% is submerged. Using the law of floatation, density = mass ÷ volume displaced = y ÷ (1.6y × 10⁻⁵) = 6.25 × 10⁴ kgm⁻³.

Using F = (9/5)C + 32, we get F = (9/5 × 60) + 32 = 140 ºF.

The smallest division on a metre rule is 1 mm. The least possible error is half of this value, which is 0.5 mm.

At absolute zero (0 K), molecular kinetic energy is zero, so the average molecular velocity is zero.

Temperature change = 20°C. Using Q = CΔθ, Q = 400 × 20 = 8000 J = 8 KJ.

In a potentiometer, the electromotive force (e.m.f.) is directly proportional to the balancing length ($L$). The relationship is given by: \[ \frac{E_1}{L_1} = \frac{E_2}{L_2} \] Given: \( E_1 = 3.06\,V \), \( L_1 = 75\,cm \) \( E_2 = 2.295\,V \) \[ L_2 = \frac{E_2 \times L_1}{E_1} = \frac{2.295 \times 75}{3.06} = 56.25\,cm \] Rounding to the nearest option gives 56.26cm.

Angular velocity (\( \omega \)) is calculated using the formula: \[ \omega = 2\pi f \] Where \( f \) is the frequency in revolutions per second (rps). Given frequency in rpm = 800. \[ f = \frac{800}{60} \, rps = \frac{40}{3} \, rps \] \[ \omega = 2 \times \pi \times \frac{40}{3} = \frac{80\pi}{3} \approx 26.666\pi \, rads^{-1} \] Approximating gives 26.7π rads\(^{-1}\).

Velocity Ratio (V.R.) is defined as the ratio of the distance moved by the effort to the distance moved by the load in the same time interval. \[ V.R. = \frac{\text{Distance moved by effort}}{\text{Distance moved by load}} \] Therefore, a V.R. of 4 means the effort moves 4 times the distance that the load moves.

In solid-state physics, the 'energy gap' or 'band gap' is the range of energy where no electron states can exist. 1. Conductors: Have overlapping valence and conduction bands (zero gap). 2. Semiconductors: Have a small energy gap (~1 eV). 3. Insulators: Have a very large energy gap (> 5 eV), making it extremely difficult for electrons to jump to the conduction band to carry current.

The color of an object is determined by the wavelengths of light it reflects. A red shirt appears red because it absorbs all other colors of white light and reflects red. When placed under pure red light, there is only red light available to be reflected. Since the shirt is highly efficient at reflecting red, it reflects almost all the incident light, appearing very bright or 'pale' (washed out) because no other colors are being absorbed to provide contrast.