MYP Physics: Electric Circuits & Current FAQ

A strong MYP response, marked against Criterion A (Knowing and Understanding), does three things:

1. States the principle — e.g. "In a series circuit, current is the same at every point."
2. Applies the formula with substituted values and units shown.
3. Interprets the result in the context given — a dimmer bulb, a tripped fuse, a specific appliance.

Quick tip: examiners specifically reward the interpretation step. A correct number with no closing sentence often loses a mark even when the calculation is right.

I tell every class the same analogy: voltage is the pressure pushing water through a pipe, current is how much water actually flows, and resistance is how narrow the pipe is. It's not perfect physics, but it gets the relationship to stick before you formalise it with V=IR.

Worked example: A 12 V battery is connected to a resistor of 4 Ω. Find the current.

I = V/R = 12/4 = 3 A

Now suppose the resistance is given as 4 kΩ instead. Convert first: 4 kΩ = 4000 Ω.

I = 12/4000 = 0.003 A = 3 mA

Common mistake: forgetting that conversion and writing 3 A again — an easy way to lose a method mark you'd otherwise keep.

Quick tip: if a question mentions "one bulb blows and the others stay on," that's your cue it's a parallel circuit — no calculation needed to answer that part.

Common mistake checklist — check these before submitting any circuit diagram:

1. Ammeters go in series with the component being measured; voltmeters go in parallel across it.
2. Battery symbol: long line = positive terminal, short line = negative.
3. Wires should meet at clear junction dots — an unmarked crossing looks like a short circuit.
4. Label every component's value (Ω, V) directly on the diagram, not in a separate list.

I've marked scripts where the physics reasoning was flawless but the diagram cost two marks purely on convention.

MYP command terms matter more than students expect. "Calculate" wants a numerical answer with working. "Explain" wants cause-and-effect reasoning. "Justify" wants you to weigh evidence and reach a supported conclusion. Using the wrong register for the command term is a quiet mark-loser across every science criterion, not just Physics.

Worked example combining two formulas: A 6 Ω heater runs on a 12 V supply. Find the power dissipated.

Step 1: I = V/R = 12/6 = 2 A

Step 2: P = IV = 2 × 12 = 24 W

This two-step chain — Ohm's Law feeding into the power equation — is one of the most common combined-calculation questions on MYP eAssessment-style circuit problems.

In my experience, the students who struggle aren't weak at maths — they're skipping the conceptual step and jumping straight to formulas. Slow down on the "why" before you calculate the "how much", and the topic gets much less intimidating.

If your child is heading toward DP Physics or DP Physics HL, a shaky grasp of series/parallel resistance at MYP level tends to resurface as a struggle with Kirchhoff's laws two years later. It's worth getting solid now rather than patching gaps under DP time pressure.

MYP Physics is graded 1-7 against four criteria: Knowing and Understanding (A), Inquiring and Designing (B), Processing and Evaluating (C), and Reflecting on the Impacts of Science (D). Circuits typically appears under Criterion A and C — knowledge application and data analysis from practical circuit investigations.

A 4-step revision routine that works for most students:

1. Re-derive V=IR from first principles rather than just memorising it.
2. Draw five circuit diagrams from a written description, no textbook open.
3. Do 10 mixed calculation questions, alternating series and parallel.
4. Write one full "explain" answer and check it against the command term expectations.

On RevisionPrep, the MYP Physics Topical Worksheets are organised exactly this way — mixed calculation and explanation questions by topic, so you're not just drilling numbers.

RevisionPrep's MYP Physics question bank and Revision Notes cover circuits and current with worked examples and mark-scheme-style model answers, so you can check not just whether your number is right but whether your explanation would actually score.

Quick tip for parents: ask your child to explain why a Christmas-light-style series circuit means one bulb going out kills the whole string, while a parallel household circuit doesn't. If they can answer that without hesitating, they understand the core concept the exam is actually testing.