IV Characteristics
I-V characteristics describe how the current (I) through a component changes as the potential difference (V) across it is varied. The relationship can be shown on a graph. For an ohmic conductor like a resistor at constant temperature, the graph is a straight line through the origin. For other components, like a filament lamp or a diode, the graph is a curve, showing that their resistance is not constant.
Full topic guide: the detailed syllabus page with worked examples and common mistakes lives at studyvector.co.uk/gcse/physics/electricity/iv-characteristics.
Topic preview: IV Characteristics
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Coverage and provenance
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Topic explanation
I-V characteristics describe how the current (I) through a component changes as the potential difference (V) across it is varied. The relationship can be shown on a graph. For an ohmic conductor like a resistor at constant temperature, the graph is a straight line through the origin. For other components, like a filament lamp or a diode, the graph is a curve, showing that their resistance is not constant.
IV Characteristics is easiest to revise when it is treated as a precise exam behaviour, not a loose note-taking category. In GCSE Physics, the goal is to recognise how the topic appears in a question, identify the command word, and decide what evidence, method, or vocabulary earns marks. StudyVector keeps this page tied to AQA · Edexcel · OCR language where coverage is available, then routes practice towards the same topic so revision moves from explanation into retrieval.
A strong revision session starts with a short recall check. Write down the rule, definition, process, or method linked to IV Characteristics before looking at any notes. Then answer one exam-style prompt and compare your answer with the mark-scheme logic: did you make a clear point, support it with the right step, and avoid drifting into a nearby topic? This matters because many lost marks come from almost-correct answers that do not match the expected structure.
Use this guide as the first layer: understand the topic, look at the worked examples, complete the mini quiz, then move into full practice. The full StudyVector practice loop is designed to capture whether mistakes are caused by knowledge, method, language, or timing. That distinction is important. If the error is factual, you need reteaching. If the error is method-based, you need a worked retry. If the error is wording, you need command-word calibration. That is how IV Characteristics becomes a controlled revision target rather than another page in a folder.
Lost marks → repair task
Why marks are usually lost here
These are the error patterns StudyVector looks for after an attempt. The goal is not a generic explanation; it is one repair move and one follow-up question.
Unit, formula, or method slip
Examiner move: Select the correct method and keep units, substitutions, signs, and rounding visible.
Repair drill: Redo the calculation or method line slowly, naming the formula before substituting values.
Missing chain of reasoning
Examiner move: Show the link between point, method, evidence, and conclusion instead of jumping to the final line.
Repair drill: Write the missing because/therefore step, then retry one isomorphic question.
Weak evidence or data reference
Examiner move: Use a precise value, quote, example, diagram feature, or syllabus term to support the claim.
Repair drill: Add one concrete reference to the answer and remove any generic sentence that does not earn a mark.
Mini quiz
Use these checks before full practice. They test topic recognition, exam technique, and whether you can connect the explanation to a marked response.
1. What should you check first when a IV Characteristics question appears in GCSE Physics?
- A.The command word and the exact topic focus
- B.The longest paragraph in your notes
- C.A memorised answer from a different topic
2. Which revision action gives the strongest evidence that IV Characteristics is improving?
- A.Rereading the explanation twice
- B.Answering a timed exam-style question and reviewing lost marks
- C.Highlighting every key phrase in the topic notes
Sample questions
Topic-specific public question previews are still being reviewed. We keep them off public pages until the topic match is safe.
Exam tips
- Read the command word carefully — "explain" needs reasons; "state" expects a short fact.
- For IV Characteristics, show structured working even when you are practising multiple choice — it builds accuracy under time pressure.
- Mark yourself against the mark scheme style: one clear point per mark, in logical order.
- Come back to this topic after a day or two; short spaced reviews beat one long cram.
Worked examples
Example 1
Modelled exam response
An I-V graph for a component is a straight line passing through the origin. When the voltage is 4V, the current is 2A. What is the resistance? Solution: Resistance R = V/I. R = 4V / 2A = 2Ω.
Example 2
Identify the task before answering
Question type: a IV Characteristics prompt asks for a clear response in GCSE Physics. Step 1: underline the command word. Step 2: name the exact part of IV Characteristics being tested. Step 3: decide whether the mark scheme wants a definition, method, explanation, comparison, or calculation. Why it works: most weak answers fail before the content starts because they answer the topic generally rather than the exact exam task.
Example 3
Turn feedback into a repair task
Suppose your answer shows partial understanding but loses marks for precision. First, rewrite the missing mark as a short target: "I need to state the mechanism, unit, reason, or evidence explicitly." Then answer one similar question without notes. Finally, compare the second attempt with the first and check whether the same mark was recovered. Why it works: IV Characteristics improves faster when feedback creates a specific retry, not another passive reading session.
Next revision routes from this subject
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Common mistakes
- Mixing up the axes on the graph. By convention, voltage (potential difference) is on the x-axis and current is on the y-axis.
- Thinking that all components have a straight-line I-V graph. Only ohmic conductors do. The curved graphs for other components are important to learn.
- Misinterpreting the gradient of the I-V graph. The gradient is I/V, which is the reciprocal of resistance (1/R). A steeper gradient means a lower resistance.
Exam board notes
Covered by all major boards (AQA, Edexcel, OCR). Higher Tier students are expected to be able to draw and interpret the I-V graphs for a resistor, filament lamp, and diode.
FAQs
What does the I-V graph for a diode look like?
A diode allows current to flow easily in one direction only. The I-V graph shows very high resistance in the reverse direction (almost zero current) and very low resistance in the forward direction once a certain threshold voltage is reached.
Why is the I-V graph for a filament lamp a curve?
As the voltage across a filament lamp increases, the filament gets hotter. This increases its resistance, so the graph curves, showing that the current increases less for each volt added.
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Full practice set
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