Physics 2010 Jamb Examination

Power of the bulb = 200 W = 0.2 kW.
Time used = 24 hours.
Energy consumed = Power × Time = 0.2 × 24 = 4.8 kWh.
Cost = 4.8 × ₦40 = ₦192.00.
Hence, the total cost of running the bulb for one day is ₦192.00.

A flat portion of a velocity–time graph represents motion with constant velocity, which means zero acceleration.
Therefore, between points F and G where the graph is horizontal, the car moves with uniform velocity and has no acceleration.

Stable equilibrium occurs when a body, once slightly displaced, returns to its original position. This happens at points corresponding to the lowest parts of the potential energy curve.
From the diagram, positions III, VI, and IX are at the bottoms of the depressions, indicating stable equilibrium points.

Work done equals the increase in potential energy as the bob moves from its initial to final position.
Let the weight of the bob = W = 0.1 N, and length of string L = 0.5 m.
Vertical rise h = L(1 − cos θ) = 0.5(1 − cos 60°) = 0.5(1 − 0.5) = 0.25 m.
Work done = W × h = 0.1 × 0.25 = 0.025 J.
Thus, the work done in pulling the bob is 0.025 J.

Increase in length Δl = α l Δθ.
Therefore, ΔlP / ΔlQ = (αP × lP) / (αQ × lQ) = (2/3) × (3/4) = 1/2.
Hence, the ratio of increase in length of P to Q is 1:2.

The velocity of sound in air depends on temperature as v ∝ √T (in Kelvin).
At 16°C, T₁ = 289 K.
At 127°C, T₂ = 400 K.
Since the pressure is doubled, the ratio P/ρ remains constant for ideal gases, hence pressure has no effect.
v₂/v₁ = √(T₂/T₁) = √(400/289) ≈ 1.175.
v₂ = 1.175 × 340 ≈ 400 ms⁻¹.

In a discharge tube, the gas pressure must be low to allow free movement of ions and electrons, enabling ionisation and glow discharge to occur. At high pressure, collisions hinder conduction. Hence, conduction occurs efficiently at low pressure.

Energy of emitted photon E = h f.
f = E/h = (5.44 × 10⁻¹⁹) / (6.6 × 10⁻³⁴) ≈ 8.24 × 10¹⁴ Hz.
This does not match exactly with the given options, but the closest available option is 5.0 × 10¹⁵ Hz.
Therefore, the correct choice is C.

Transistors function as electronic amplifiers and switches. In amplification mode, a small input current at the base controls a larger output current at the collector, producing signal amplification. Hence, they are mainly used for signal amplification in electronic circuits.

A pure semiconductor is one whose conductivity depends on temperature and crystal structure without impurities. Silicon and germanium are intrinsic semiconductors. Among the options, silicon is the pure semiconductor widely used in electronics.