GCE Physics
Past Questions

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## The reasoning The **unit of electric current** is the **Ampere (A)**, named after French physicist André-Marie Ampère. Think of it this way: Current is the **flow of electric charge** — specifically, how much charge passes through a point per second. One ampere means one coulomb of charge flowing past a point every second (I = Q/t). The principle here is **knowing what each electrical quantity measures**: - **Current (I)** = flow of charge → **Ampere (A)** - Voltage (V) = electrical pressure → Volt (V) - Resistance (R) = opposition to flow → Ohm (Ω) - Power (P) = rate of energy transfer → Watt (W) ## Why the wrong options tempt you **A) Volt** — This measures electrical potential difference (voltage), not current. It's easy to mix up because both are fundamental electrical quantities. **B) Ohm** — This measures resistance. Students confuse it with current because of Ohm's Law (V = IR), where all three appear together. **D) Watt** — This measures power (energy per second). It's related to current (P = VI), but it's not the unit of current itself. ## Quick takeaway **"Amps measure the flow, Volts push it, Ohms slow it, and Watts show the power."** Remember: **A**mpere for **A**mount of current flowing!

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**The reasoning** Sound is a **mechanical wave** — it travels by making particles vibrate and bump into their neighbors. Think of it like a "push" passing through a crowd: each person nudges the next. For this to work, you need *something* with particles that can vibrate — that "something" is called a **medium**. The medium can be: - **Solid** (sound travels through walls, your desk) - **Liquid** (you can hear underwater) - **Gas** (sound travels through air to your ears) No particles? No sound. That's why astronauts in space can't hear each other scream — space is a vacuum with no medium. **Why the wrong options tempt you** - **A) Vacuum** — This is the *opposite* of what sound needs. Space is silent! - **C) Heat** — Temperature affects sound *speed*, but isn't required for sound to exist - **D) Light** — Light is an electromagnetic wave that *doesn't* need a medium; sound does **Quick takeaway** "Sound waves need particles to vibrate — no medium, no sound; that's why space is silent."

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**The reasoning** "Half of 60" means dividing 60 into two equal parts. In mathematical terms: **Half of 60 = 60 ÷ 2 = 30** Think of it this way: If you have ₦60 and want to share it equally between two people, each person gets ₦30. That's what "half" means — one out of two equal parts. The principle here is **division by 2**. Whenever you see "half of [any number]," you're simply dividing that number by 2. **Why the wrong options tempt you** - **A) 20** — This would be one-third of 60 (60 ÷ 3), not half. Easy mix-up if you rush! - **C) 40** — This is two-thirds of 60. You might pick this if you mistakenly subtract 20 instead of dividing. - **D) 50** — This comes from subtracting 10 from 60, which isn't finding half — it's just subtraction without logic. **Quick takeaway** "Half of any number" always means **divide by 2** — master this and you'll never fall for fraction tricks again!

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## The reasoning **Specular reflection** happens when light bounces off a *smooth, polished surface* like a mirror, calm water, or glass. The key principle here is the **Law of Reflection**: the angle of incidence equals the angle of reflection, and all rays remain **parallel and organized**. Because the reflected rays stay orderly and don't scatter, they can converge at your eye to form a **clear, sharp image** — exactly what you see when you look in a bathroom mirror. The smoothness preserves the relationship between light rays, so the image isn't distorted. ## Why the wrong options tempt you **A) Diffuse rays** — This is what *rough* surfaces (like paper or unpolished wood) produce. They scatter light in all directions, which is the opposite of specular reflection. **C) No image** — Tempting if you confuse reflection with refraction or absorption, but mirrors definitely form images! **D) Heat only** — Light can produce heat, but reflection's main job is redirecting light rays, not converting them to thermal energy. ## Quick takeaway **Smooth surfaces = specular reflection = sharp images.** Think: mirror-smooth means mirror-clear! 🪞

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**The reasoning** This isn't a multiple-choice question — it's asking you to **define and explain** two fundamental physics concepts: **Velocity** is the rate of change of displacement with time. It tells you how fast something is moving *and in what direction*. Formula: **v = Δs/Δt** (displacement ÷ time). SI unit: **metres per second (m/s)**. **Acceleration** is the rate of change of velocity with time. It tells you how quickly velocity itself is changing. Formula: **a = Δv/Δt** (change in velocity ÷ time). SI unit: **metres per second squared (m/s²)**. Notice both are *vector quantities* — direction matters! **Why this format matters** WAEC and JAMB often mix MCQs with "theory" questions requiring definitions. Students sometimes panic and write vague answers like "velocity is speed" (wrong — speed has no direction) or forget the SI units entirely. Always state the definition clearly, then add the unit. **Quick takeaway** Velocity = displacement per time (m/s); Acceleration = velocity change per time (m/s²) — both need direction to be complete.

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Electric current is measured in amperes (A). Volt is potential difference; ohm is resistance; watt is power.

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V = IR (voltage = current × resistance) is Ohm's law for resistive circuits.

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Velocity is a vector. Even at constant speed, changing direction in circular motion means velocity (and so acceleration) changes.

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Object at centre of curvature (2f) gives a real, same-size image. So 2f = 20 → f = 10 cm.

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Sound travels at about 330–340 m/s in dry air at room temperature.

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Power = work/time (or energy/time). SI unit: watt (W) = 1 J/s.

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Vector quantities have both magnitude and direction (velocity, force). Scalars have only magnitude (mass, temperature).

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Electron charge = −1.6 × 10⁻¹⁹ coulombs (negative).

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Velocity and displacement are both vector quantities because they have both magnitude and direction. Speed and energy are scalars, and mass is also a scalar quantity.

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The mean diameter is calculated as (2.53 + 2.55 + 2.54 + 2.54) / 4 = 10.16 / 4 = 2.54 mm. Averaging repeated measurements reduces random error and gives the best estimate of the true value.

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Pressure = Force/Area. Force has dimensions $MLT^{-2}$ and Area has dimensions $L^{2}$, so Pressure = $MLT^{-2} / L^{2} = ML^{-1}T^{-2}$. This is the correct dimensional formula for pressure.

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The SI prefix 'nano' (symbol: n) represents a factor of $10^{-9}$. For example, 1 nanometre (nm) = $10^{-9}$ m. Micro ($10^{-6}$), pico ($10^{-12}$), and milli ($10^{-3}$) are different prefixes.

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The Kelvin (K) is one of the seven SI base units, used to measure thermodynamic temperature. Newton, Joule, and Pascal are all derived units formed from combinations of base units.