You recognise the formula on the board. The teacher’s solution makes sense. Then a question changes the numbers or adds another component, and you don’t know where to begin. Physics problem solving needs a bridge between reading the question and calculating an answer. This guide builds that bridge with three circuit examples. They practise general secondary-school skills, including skills useful to Thanaweya Amma students; they are not official examination questions or a claim about the current Egyptian syllabus. Keep your school’s current topic list beside you, and use the examples to practise a method you can explain in your own words.
Write the unknown, label the given quantities, sketch the situation and choose a relationship before entering numbers. Our three circuit examples separate equation choice, unit conversion and combining resistors. Record the first step that went wrong, then solve a fresh question that tests that step.
Physics practice: what active-learning research found
Solving and explaining physics problems gives your tutor something to diagnose. A large university STEM review offers useful context for making lessons more participatory.
studies analysed
Undergraduate STEM studies in the 2014 meta-analysis.
Freeman et al. · PNAS, 2014 — original sourceaverage failure rate: lectures
Reported for traditional lecturing in the analysed courses.
Freeman et al. · PNAS, 2014 — original sourceaverage failure rate: active learning
Reported for active-learning courses in that review.
Freeman et al. · PNAS, 2014 — original sourceBring an unfinished solution to your physics lesson. Explain why you chose each equation, let the tutor identify the first faulty step, then solve another problem with changed values and conditions.
Context: Freeman et al., 2014: undergraduate science, technology, engineering and mathematics. These are not Egyptian secondary-school pass rates or a trial of this guide. The 12-percentage-point difference is not a predicted improvement in your exam score.
Why does recognising a physics formula feel easier than solving a problem?
Recognising a formula gives you a familiar pattern; solving requires choosing when that pattern applies. Start by naming the quantity you need. “Find the current” is a clearer instruction to yourself than “use the electricity formula.” Then write the given voltage and resistance beside their units.
A useful check is to cover the numbers and describe the situation first. Can you say which component the voltage is measured across? Is the stated resistance for one component or the whole circuit? If you cannot explain the setup, calculation will hide the gap instead of resolving it.
Keep your first attempt, including crossed-out lines. A tutor can learn more from the point where your reasoning changes direction than from a copied correct solution. Write a specific question beside that point: “Why can these resistances be added?” gives you something concrete to discuss.
| What went wrong? | What to practise next |
|---|---|
| I did not know what to find | Translate the last sentence into a named unknown. |
| I chose the wrong equation | Explain the physical situation without numbers. |
| I used the wrong units | Write a conversion line before substitution. |
| My equation was right but my answer was wrong | Check rearrangement and calculator entry separately. |
How should you start a physics problem?
Use a short written routine that makes your decisions visible. Write the unknown first, then the known quantities, a sketch, the relevant relationship and a symbolic rearrangement. Only substitute numbers once the equation already has the unknown on its own. Finish with units and a reasonableness check.
For the ideal ohmic resistors used here, voltage, current and resistance are related by V = IR. OpenStax explains this relationship and its limits: do not assume that every electrical component behaves as an ohmic resistor. The model matters as much as the formula.
- Unknown: what quantity is requested, and in which unit?
- Knowns: copy values together with their units.
- Sketch: label components, connections and measurements.
- Relationship: explain why it fits this setup.
- Rearrange: isolate the unknown before substituting.
- Check: inspect units, arithmetic and physical sense.
Worked example: find the current through one resistor
Suppose an ideal 6 Ω resistor has a potential difference of 12 V across it. Find the current through that resistor. This is an practice problem: the useful decision is identifying that the given voltage and resistance refer to the same component, so I = V/R applies.
Before calculating, ask what would happen if the resistance increased while the voltage stayed fixed. The current should decrease. That observation helps you reject the tempting but incorrect expression I = V × R. A calculator can evaluate either expression; it cannot choose the physical relationship for you.
practice: 12 V across 6 Ω
- Unknown: current I in amperes.
- Knowns: V = 12 V and R = 6 Ω.
- Rearrange V = IR to I = V/R.
- Substitute: I = 12/6 = 2 A.
- Check: doubling R to 12 Ω would reduce I to 1 A at the same voltage.
How do you stop unit conversions losing the answer?
Convert values into compatible units before substitution and show the conversion on its own line. In this example, a resistor carries 250 mA with 5 V across it. Because 1 A equals 1,000 mA, use 0.250 A in R = V/I to obtain resistance in ohms.
The most revealing check is to compare the incorrect and correct routes. Dividing 5 by 250 produces 0.02, but the current was not supplied in amperes. Carrying units through the calculation would expose that mismatch. Labelled quantities help prevent an apparently tidy numerical answer from passing unnoticed.
practice: convert before dividing
- 250 mA = 250/1,000 A = 0.250 A.
- R = V/I = 5/0.250 = 20 Ω.
- Reverse check: IR = 0.250 × 20 = 5 V.
- Fresh question: 6 V across a component carrying 300 mA gives R = 6/0.300 = 20 Ω.
Worked example: turn a series circuit into a simpler problem
For ideal resistors connected in series, add their resistances before finding the current through the circuit. OpenStax explains that the same current passes through each series component. Our example uses a 12 V ideal source, a 2 Ω resistor and a 4 Ω resistor, with negligible wire resistance.
Notice the extra decision: identify the connection before selecting the equivalent-resistance rule. Adding the resistance values is appropriate here because the components are in series. It is not a general shortcut for every diagram containing two resistors. Redraw a confusing diagram as a single path before calculating.
practice: two resistors in one path
- Equivalent resistance: R = 2 + 4 = 6 Ω.
- Circuit current: I = 12/6 = 2 A.
- Voltage across 2 Ω: V₁ = 2 × 2 = 4 V.
- Voltage across 4 Ω: V₂ = 2 × 4 = 8 V.
- Check: 4 + 8 = 12 V, matching the source voltage.
How can you tell whether you can solve it independently?
Try a changed problem without looking at the worked solution, then explain your first decision aloud. Reproducing familiar numbers can disguise reliance on memory. Change the unknown or the units, keep the same physical model and see whether you can rebuild the method from the question.
Use these checks: an 18 V supply across 9 Ω gives 2 A; a resistor carrying 0.4 A with 8 V across it has resistance 20 Ω; series resistors of 3 Ω and 5 Ω across 16 V carry 2 A. Their voltage drops are 6 V and 10 V.
If you get stuck, reveal only the next missing decision rather than the entire answer. Then close the solution and restart on a blank page. Save the independent attempt with a short note explaining what changed. That note becomes the starting point for your next revision session.
Bring your reasoning to the next physics lesson
Choose one error pattern for your next lesson and bring an attempted question showing it. “I need help with physics” covers too much ground. “I can use Ohm’s law, but I cannot identify the voltage across a particular resistor” makes the next explanation and practice task much more focused.
Print the questions below or copy them onto a blank worksheet. Use them with current school materials, then ask your teacher which topics and conventions apply to your course. When comparing secondary-school physics tutors, confirm the curriculum and year they teach and ask how they review students’ independent working.
Work through physics problems with a tutor
Find Physics tutors and share a problem you could not finish. Ask whether the tutor teaches your school curriculum and can review your reasoning step by step.
Make it your own
Check things off as you go. Your selections last while this page is open.
A few more answers.
Should I memorise more physics formulas?
Memorisation helps when you also know what the symbols mean and when a relationship applies. For each formula, write one suitable situation and one limitation. Then practise choosing the relationship without calculating. If the equation is correct but the answer is wrong, focus on rearrangement or units instead.
Are these official Thanaweya Amma questions?
No. These are general secondary-school circuit exercises. They illustrate a problem-solving method and do not represent the current Egyptian examination specification. Confirm your required topics, symbols and question formats with your current school materials or teacher before using any revision resource as course coverage.
What should I do when I understand the solution but cannot start alone?
Cover the worked solution and write only the unknown, known quantities and sketch. Identify the first line you cannot produce independently. Ask for help with that decision, then attempt a changed question. The goal is to reconstruct the reasoning, rather than remember the appearance of a completed answer.
Sources & further reading
Explore the original resources for more detail. Practice examples in this guide are illustrative, not official examination questions.
OpenStax Physics: Ohm’s lawOpenStax Physics: series circuitsYour questions. The right teacher.
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