Edexcel GCSE Physics Topic 1: Key Concepts of Physics Exam Questions

About Edexcel GCSE Physics Topic 1: Key Concepts of Physics

Topic 1 is the toolkit that sits underneath every other part of Edexcel GCSE Physics. It covers the base SI units, derived units, prefixes from nano to giga, standard form and sensible use of significant figures. Because these skills are needed everywhere, Topic 1 is assessed on both Paper 1 and Paper 2, usually inside questions about other topics rather than as stand-alone questions. Examiners test whether you can convert units before substituting into an equation, rearrange formulae, give answers to an appropriate number of significant figures and quote the correct unit. Small slips here cost marks in calculations right across the course.

What you need to know

• SI base units Learn the base units you meet at GCSE: metre (m), kilogram (kg), second (s), ampere (A), kelvin (K) and mole (mol). Derived units such as the newton, joule, watt, volt, ohm and hertz are built from these.
• Prefixes Know giga (10^9), mega (10^6), kilo (10^3), centi (10^-2), milli (10^-3), micro (10^-6) and nano (10^-9). Convert to the base unit before using an equation, for example 450 mA = 0.45 A and 2.5 km = 2500 m.
• Standard form Write very large and very small numbers as a number between 1 and 10 multiplied by a power of ten, such as 0.00047 = 4.7 x 10^-4. Be confident entering standard form on your calculator.
• Significant figures Give your final answer to the same number of significant figures as the least precise data in the question, usually 2 or 3. Do not round in the middle of a calculation.
• Rearranging equations Change the subject of an equation before substituting, for example v = x / t becomes x = v x t. Show the equation, the substitution and the answer with unit to collect all the marks.
• Units of time and energy Convert minutes and hours into seconds for most equations (1 hour = 3600 s). Recognise that kilowatt-hours are a unit of energy used on electricity bills.

Common mistakes in Topic 1: Key Concepts of Physics

• Substituting values in non-SI units, such as minutes or kilometres, straight into an equation. Convert to seconds and metres first.
• Rounding part-way through a multi-step calculation. Keep the full calculator value and only round the final answer.
• Writing standard form incorrectly, for example 47 x 10^-5 instead of 4.7 x 10^-4. The first number must be between 1 and 10.
• Leaving out the unit or giving the wrong one, such as writing W for energy. Always state the unit of the quantity you have calculated.
• Confusing milli (10^-3) with micro (10^-6). Check the prefix symbol carefully: m means milli and the Greek letter mu means micro.

Try three Topic 1: Key Concepts of Physics exam-style questions