alculatorUse":null,"parts":[{"id":"19ce47e9-a7e1-41ae-aa02-a9d60541f7cc","label":null,"content":"Explain:\n* how and why static electric charge builds up during this delivery and why this is dangerous\n* how this hazard is mitigated in the facility.","markscheme":"- Friction between the moving flour particles and the inner surface of the non-conducting polymer pipe causes the transfer of electrons. B1\n- This transfer of electrons results in a significant build-up of static charge on the pipe walls and the silo components. B1\n- The accumulated static charge creates a high potential difference (voltage) between the charged components and nearby earthed objects. B1\n- This high potential difference can discharge by ionizing the surrounding air, creating an electrical spark. B1\n- The spark provides the activation energy to ignite the highly flammable flour dust suspension, potentially causing a catastrophic dust explosion. B1\n- To mitigate this hazard, all metal components (silo, pipe joints, tanker) are bonded together and connected to earth with high-conductivity metal (e.g., copper) wires, which allows electrons to flow safely to the ground and prevents charge build-up. B1","marks":6,"order":0,"markingRubric":null,"explanation":{"methods":[{"id":"charge_and_earthing","label":"Charge build-up and earthing","steps":[{"type":"text","order":1,"title":"Identify the charging process","content":"The flour is blown quickly along the **non-conducting polymer pipe**. As particles rub against the pipe's inner surface, **friction transfers electrons** between the flour and the pipe. This is charging by friction.\n\nStating electron transfer, rather than simply saying “friction makes charge”, earns the first mark.","highlights":[{"text":"blown pneumatically at high speed through a non-conducting polymer pipe","location":"specification"}]},{"type":"text","order":2,"title":"Explain the charge build-up","content":"Because the polymer is an **insulator** (a material in which electrons cannot move freely), charge does not flow away easily. It accumulates as static charge on the pipe walls and on components of the silo system.\n\nThis explicit link from electron transfer to a significant static charge build-up earns the second mark.","highlights":[{"text":"non-conducting polymer pipe","location":"specification"}]},{"type":"text","order":3,"title":"Link charge to voltage","content":"The accumulated charge produces a large **potential difference (voltage)** between charged parts of the equipment and nearby objects connected to Earth. Potential difference is the energy transferred per unit charge, so a large value can drive a discharge.\n\nNaming the high potential difference between the charged equipment and earthed objects earns the third mark.","highlights":[{"text":"large metal storage silo","location":"specification"}]},{"type":"text","order":4,"title":"Explain the spark","content":"If the potential difference becomes high enough, it **ionises the air**: electrons are removed from air particles, allowing charge to cross the gap suddenly. This electrical discharge is a spark.\n\nThe cause-and-effect statement “high voltage ionises air, producing a spark” earns the fourth mark."},{"type":"text","order":5,"title":"State the explosion risk","content":"The silo contains a suspended mixture of fine flour dust and air, which is highly explosive. A spark supplies the **activation energy** needed to ignite the dust, so it could trigger a catastrophic dust explosion.\n\nLinking the spark to ignition of the dust suspension earns the fifth mark.","highlights":[{"text":"Fine flour dust suspended in the air inside the silo forms a highly explosive mixture.","location":"specification"}]},{"type":"text","order":6,"title":"Earth the metalwork","content":"All the metal components — the silo, pipe joints and tanker — are **bonded** (joined electrically) together and connected to Earth using high-conductivity metal wires such as copper. Bonding holds the

Charging by friction and electrostatic phenomena

Question 3

Charging by friction and electrostatic phenomena Questions

Charging by friction and electrostatic phenomena

Question 3

Charging by friction and electrostatic phenomena Questions