Physics 2017 Jamb Examination

A manometer is specifically designed to measure gas pressure. A barometer measures atmospheric pressure, a thermometer measures temperature, and a hydrometer measures the relative density of liquids.

Power is the rate of doing work. Work done against gravity is \( mgh \).\[ P = \frac{mgh}{t} \]\[ P = \frac{50 \times 10 \times 5}{5} \]\[ P = 500\text{W} \]

Using the wave equation \( v = f\lambda \):
Given:
\( v = 3 \times 10^8 \text{ ms}^{-1} \)
\( f = 600 \text{ kHz} = 600,000 \text{ Hz} = 6 \times 10^5 \text{ Hz} \)\[ \lambda = \frac{v}{f} = \frac{3 \times 10^8}{6 \times 10^5} \]\[ \lambda = 0.5 \times 10^3 = 500\text{m or } 5.0 \times 10^2\text{m} \]

Scalar quantities have magnitude only, while vector quantities have both magnitude and direction. Tension, weight (a force), and impulse are all vectors because they act in specific directions. Mass is a scalar as it only describes the quantity of matter regardless of direction.

The power (P) of a lens is the reciprocal of its focal length (f) in metres.\[ P = \frac{1}{f} \implies f = \frac{1}{P} \]\[ f = \frac{1}{5.0} = 0.2\text{m} \]

According to Hooke's Law, \( F = ke \). First, find the force for the 0.8kg load:
\( F_1 = mg = 0.8 \times 10 = 8\text{N} \).
Since force is proportional to extension (\( F \propto e \)):\[ \frac{F_1}{e_1} = \frac{F_2}{e_2} \implies \frac{8}{0.04} = \frac{16}{e_2} \]\[ e_2 = \frac{16 \times 0.04}{8} = 2 \times 0.04 = 0.08\text{m} \]

Eddy currents are circulating currents induced in solid conductors by a changing magnetic field. To minimize energy loss (heat) from these currents in transformers or motors, the core is made of thin, insulated laminations (sheets or wires) of soft iron rather than a single solid block. This breaks the large loops of current into much smaller ones, increasing effective resistance and reducing heat loss.

Assuming standard values from this 2017 problem: C = 4\(\mu\)F (\(4 \times 10^{-6}\)F) and V = 20V.
Energy (W) = \( \frac{1}{2}CV^2 \)\[ W = 0.5 \times (4 \times 10^{-6}) \times 20^2 \]\[ W = 0.5 \times 4 \times 10^{-6} \times 400 \]\[ W = 800 \times 10^{-6} = 8.0 \times 10^{-4}\text{J} \]

Impulse is equal to the change in momentum (\( Ft = \Delta p \)).
Since it starts from rest (initial momentum = 0), final momentum equals the impulse.\[ \text{Momentum} = F \times t \]\[ \text{Momentum} = 5\text{N} \times 5\text{s} = 25\text{kgms}^{-1} \]

Refraction (bending when changing medium), interference (overlapping of waves), and diffraction (spreading around obstacles) are fundamental wave properties shared by all waves, including mechanical waves (sound/water) and electromagnetic waves (light). Polarization is the only property typically restricted to transverse waves.