OCR GCSE Physics A: Static electricity and electric fields (J249) – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover OCR GCSE Physics A (Gateway Science, J249), specification Version 5.0 (July 2026), learning outcomes P3.1a to P3.1d. Questions and parts marked (Higher Tier only) test P3.1d, which is Higher Tier only. All other questions cover content assessed in both tiers. Read the study guide first, or use the revision notes. Course links: OCR GCSE Physics hub, printable checklist and free 10-minute diagnostics.

Questions

1. State the two types of electric charge, and state the net charge on an object that has equal amounts of each. [2]

2. A plastic comb is rubbed on dry hair and becomes negatively charged. Explain, in terms of electrons, why the comb and the hair both become charged. [3]

3. In a simple model, a plastic strip and a cloth each have 30 positive units and 30 negative units of charge before rubbing. One electron is -1 unit. During rubbing, 8 electrons move from the cloth to the strip.

(a) Calculate the net charge on the strip after rubbing. [2] (b) State the net charge on the cloth. [1] (c) Show that the total charge has not changed. [1]

4. Two identical polythene strips are each rubbed with the same dry cloth. They are hung from separate threads so that they are 3 cm apart and not touching.

(a) Describe what happens to the strips. [1] (b) Explain why this is evidence for a force between charged objects that are not in contact. [2] (c) The strips are moved closer together. State how the force between them changes. [1]

5. A student holds a copper rod in her hand and rubs it with a cloth. She finds that the rod shows no sign of charge. Explain why, and suggest one change to the method that would let the rod keep a charge. [3]

6. A balloon is rubbed on a jumper and becomes negatively charged. It is held against a wall that has no net charge and it stays there. Explain why the balloon is attracted to the wall. [4]

7. A gold leaf electroscope is uncharged, with the leaf hanging down. A negatively charged rod is brought close to the metal cap without touching it.

(a) The leaf rises. Explain why. [3] (b) The rod is taken away and the leaf falls. Explain why. [1] (c) The experiment is repeated, but this time the rod touches the cap before it is taken away. The leaf stays raised. Explain why. [2]

8. (Higher Tier only) Describe the electric field around an isolated negatively charged sphere, and state where the field is strongest. [3]

9. (Higher Tier only) Two equal positive spheres are placed a short distance apart.

(a) Describe the pattern of field lines. [2] (b) State what the field is like midway between the spheres. [1] (c) Use the idea of an electric field to explain why the spheres repel each other. [2]

10. (Higher Tier only) A student places two metal electrodes in a shallow dish of castor oil and sprinkles semolina on the surface. When the electrodes are connected to a high-voltage supply, the grains line up in curved lines from one electrode to the other. The lines are close together near the electrodes and further apart near the edge of the dish.

(a) State what the lines of grains represent. [1] (b) Say where the field is strongest, and give the reason. [2] (c) The grains do not show which way the arrows on the field lines point. Explain how you would decide the direction. [2] (d) The dish shows the field as a flat pattern. State one limitation of this as a model of the real field. [1] (e) The connections to the supply are swapped over. State what changes in the field diagram. [1]

11. A student stands on an insulating stool and touches a Van de Graaff generator dome that is being charged. The dome becomes negative, and her hair stands out from her head. Later, a spark jumps from the dome to a nearby earthed metal sphere.

(a) Explain, in terms of electrons, what it means for the dome to be negative. [2] (b) Explain why the strands of her hair move apart. [2] (c) Explain why she must stand on an insulating stool. [1] (d) State what the spark does to the charge on the dome. [1] (e) (Higher Tier only) Explain, using the idea of an electric field, why the spark happens. [2]

Answers

1. Positive and negative [1]; the net charge is zero [1] [2] Examiner insight: Name both types. “Positive” alone is not a complete answer to a question that asks for two.

2. Comb and hair are insulators, and electrons move from the hair to the comb [1]; the comb gains electrons, so it has more negative than positive charge [1]; the hair loses the same number of electrons, so it is left positive [1] [3] Examiner insight: A strong answer says which way the electrons move. It never says protons or positive charge moved.

3. (a) Negative units on the strip are now 30 + 8 = 38 [1]; net charge = 30 - 38 = -8 units [1] (b) The cloth has 30 - 8 = 22 negative units and 30 positive units, so the net charge is +8 units [1] (c) -8 + 8 = 0, the same as the total before rubbing (0 + 0), so charge is moved, not made [1] [4] Examiner insight: Check the sign as well as the size. Gaining electrons gives a negative net charge, so a final answer of +8 on the strip would lose the credit.

4. (a) The strips move apart (they repel) [1] (b) The strips push on each other even though there is air between them and nothing touches [1]; the force acts at a distance, so it is a non-contact force [1] (c) The force increases [1] [4] Examiner insight: For “evidence” questions, say what you see and then what it shows. “They repel” alone does not mention that nothing is touching.

5. Copper is a conductor [1]; any charge made flows away through her body to the ground [1]; hold the rod with an insulating handle (or wear insulating gloves) so the charge cannot flow away [1] [3] Examiner insight: The answer needs to say where the charge goes. “Copper is a conductor” with no consequence is incomplete.

6. The balloon has extra electrons [1]; the electrons in the wall’s surface atoms shift slightly away from the balloon [1]; the wall surface nearest the balloon becomes slightly positive [1]; the attraction to these nearer positive charges is greater than the repulsion from the farther negative ones, so the balloon is pulled to the wall, which is still neutral overall [1] [4] Examiner insight: The wall does not need to be charged. Saying the wall “is positive” loses credit, because its net charge is zero.

7. (a) Electrons in the metal are repelled by the negative rod [1]; they move down to the stem and leaf, which both become negative [1]; like charges repel, so the leaf lifts away from the stem [1] (b) The electrons move back when the rod is removed, so the leaf and stem are no longer charged [1] (c) Some electrons pass from the rod to the electroscope [1]; the electroscope now has a net negative charge that stays after the rod is removed, so the leaf stays raised [1] [6] Examiner insight: Part (c) needs a statement about electrons moving onto the electroscope, which is the difference from part (a), where the total charge stays zero.

8. The field lines are straight and evenly spaced around the sphere [1]; the arrows point inwards, towards the sphere [1]; the field is strongest close to the sphere, where the lines are closest together [1] [3] Examiner insight: The arrows must be described. Lines with no direction do not show whether the sphere is positive or negative.

9. (a) The lines curve away from each other [1]; no lines cross, and the lines start on the spheres and point outwards [1] (b) The field is very weak midway between them (zero for equal charges) [1] (c) Each sphere is in the field of the other [1]; the field gives a force on it directed away from the other sphere, so they repel [1] [5] Examiner insight: In (c), name the sphere that is the source of the field and the sphere that feels the force. “The fields repel” is too vague.

10. (a) The lines of grains show the shape of the electric field lines [1] (b) The field is strongest near the electrodes [1]; the lines are closest together there [1] (c) Field lines are drawn with arrows showing the force on a positive charge, so they run from the positive electrode to the negative electrode [1]; you need to know which electrode is connected to the positive terminal of the supply [1] (d) The real field exists in three dimensions, but the grains show only a flat slice on the surface of the oil [1] (e) The arrows reverse direction, but the shape of the pattern stays the same [1] [7] Examiner insight: In (d) a limitation must be about the model. Comments about messy technique, such as grains being uneven, do not answer the question.

11. (a) The dome has gained electrons [1]; it has more negative than positive charge [1] (b) Each strand of hair has the same type of charge [1]; like charges repel, so the strands move apart [1] (c) A person standing on the ground, or on a conductor, would let the charge flow away through the body to earth [1] (d) The dome loses some or all of its charge, as charge flows across the gap [1] (e) Charge on the dome makes the field between the dome and the sphere stronger [1]; when the field is strong enough, the air in the gap can no longer insulate and charge crosses it as a spark [1] [8] Examiner insight: For (e), say what the field does and what happens to the air. The words “charge jumps” on their own describe the spark but do not use the field.

Where marks are usually lost

• Saying protons or positive charges move, when only electrons are transferred.
• Giving the sign of a net charge the wrong way round after electrons are gained or lost.
• Leaving out the equal and opposite charge on the second object when explaining rubbing.
• Describing a force between charged objects without saying that nothing is in contact.
• Calling the wall, or another neutral object, charged when explaining attraction to a charged balloon.
• Saying “the metal is a conductor” without saying that charge flows away to the ground.
• Drawing field lines without arrows, with crossing lines, or with arrows pointing the wrong way for the sign of the charge.
• Saying “strong field” without linking it to lines being close together.
• Mixing up the direction of the force on an electron with the arrow direction.

Next steps

• Read the revision notes for a short recap.
• Re-read the study guide for any part that felt weak.
• Go to the OCR GCSE Physics hub and tick off outcomes on the printable checklist.
• Try the free 10-minute diagnostics.
• Book a free trial class.

Official syllabus

OCR GCSE (9-1) Gateway Science Physics A (J249), Version 5.0 (July 2026), for first assessment in 2018, published by OCR. These questions cover learning outcomes P3.1a to P3.1d.