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Fields About this practice Gravitational, electric and magnetic fields.
Physics: Standard Level Fields
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1 State Newton's law of gravitation, and use it to explain why gravitational force decreases with the square of separation. Easy 3 marks No calculator + 2 Marking analysis: A learner attempts the following task: “State Newton's law of gravitation, and use it to explain why gravitational force decreases with the square of separation.” Their response addresses only this point: “States F = Gm₁m₂/r², where G is the gravitational constant.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks. Marking analysis Easy 3 marks No calculator + 3 Calculate the gravitational field strength at the surface of a planet of mass 4.0 × 10²⁴ kg and radius 5.0 × 10⁶ m. Use G = 6.67 × 10⁻¹¹ N m² kg⁻². Easy 3 marks Calculator + 4 Marking analysis: A learner attempts the following task: “Calculate the gravitational field strength at the surface of a planet of mass 4.0 × 10²⁴ kg and radius 5.0 × 10⁶ m. Use G = 6.67 × 10⁻¹¹ N m² kg⁻².” Their response addresses only this point: “Uses g = GM/r².” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks. Marking analysis Easy 3 marks Calculator + 5 Define electric field strength, and state its direction relative to a positive test charge. Easy 2 marks No calculator + 6 Marking analysis: A learner attempts the following task: “Define electric field strength, and state its direction relative to a positive test charge.” Their response addresses only this point: “Defines electric field strength as the electric force per unit positive charge experienced at a point.” Evaluate the response against the complete 2-mark task. Identify what earns credit and state every additional requirement needed for full marks. Marking analysis Easy 2 marks No calculator + 7 Two point charges of +3.0 μC and −3.0 μC are separated by 0.20 m. Calculate the magnitude of the electric force between them. Use k = 8.99 × 10⁹ N m² C⁻². Easy 3 marks Calculator + 8 Marking analysis: A learner attempts the following task: “Two point charges of +3.0 μC and −3.0 μC are separated by 0.20 m. Calculate the magnitude of the electric force between them. Use k = 8.99 × 10⁹ N m² C⁻².” Their response addresses only this point: “Uses Coulomb's law F = kq₁q₂/r².” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks. Marking analysis Easy 3 marks Calculator + 9 Explain why a charged particle moving parallel to a uniform magnetic field experiences no magnetic force, while one moving perpendicular to the field does. Easy 3 marks No calculator + 10 Marking analysis: A learner attempts the following task: “Explain why a charged particle moving parallel to a uniform magnetic field experiences no magnetic force, while one moving perpendicular to the field does.” Their response addresses only this point: “States that the magnetic force on a moving charge is given by F = qvB sinθ, where θ is the angle between velocity and field.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks. Marking analysis Easy 3 marks No calculator + 11 A charged particle moves in a circular path perpendicular to a uniform magnetic field. State the direction of the magnetic force at any instant, relative to the particle's velocity. Easy 2 marks No calculator + 12 Marking analysis: A learner attempts the following task: “A charged particle moves in a circular path perpendicular to a uniform magnetic field. State the direction of the magnetic force at any instant, relative to the particle's velocity.” Their response addresses only this point: “States that the magnetic force is always perpendicular to the particle's velocity.” Evaluate the response against the complete 2-mark task. Identify what earns credit and state every additional requirement needed for full marks. Marking analysis Easy 2 marks No calculator + 13 Define gravitational potential energy in a radial field, and explain why it is defined to be negative for a mass at a finite distance from another mass. Easy 3 marks No calculator + 14 Marking analysis: A learner attempts the following task: “Define gravitational potential energy in a radial field, and explain why it is defined to be negative for a mass at a finite distance from another mass.” Their response addresses only this point: “Defines gravitational potential energy as the work done to bring a mass from infinity to a point in the gravitational field.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks. Marking analysis Easy 3 marks No calculator + 15 A satellite orbits Earth in a circular orbit of radius r. Show that its orbital period T satisfies T² ∝ r³, using Newton's law of gravitation and the centripetal force equation. Medium 4 marks No calculator + 16 Marking analysis: A learner attempts the following task: “A satellite orbits Earth in a circular orbit of radius r. Show that its orbital period T satisfies T² ∝ r³, using Newton's law of gravitation and the centripetal force equation.” Their response addresses only this point: “Equates gravitational force to the required centripetal force: GMm/r² = mv²/r (or equivalently mω²r).” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks. Marking analysis Medium 4 marks No calculator + 17 A parallel plate capacitor has a uniform electric field of 2000 V m⁻¹ between its plates, which are 0.050 m apart. Calculate the potential difference between the plates. Easy 3 marks Calculator + 18 Marking analysis: A learner attempts the following task: “A parallel plate capacitor has a uniform electric field of 2000 V m⁻¹ between its plates, which are 0.050 m apart. Calculate the potential difference between the plates.” Their response addresses only this point: “Uses E = V/d for a uniform field between parallel plates.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks. Marking analysis Easy 3 marks Calculator + 19 Compare the direction of the gravitational force between two masses with the direction of the electric force between two like (same-sign) charges. Easy 2 marks No calculator + 20 Marking analysis: A learner attempts the following task: “Compare the direction of the gravitational force between two masses with the direction of the electric force between two like (same-sign) charges.” Their response addresses only this point: “States that the gravitational force between two masses is always attractive.” Evaluate the response against the complete 2-mark task. Identify what earns credit and state every additional requirement needed for full marks. Marking analysis Easy 2 marks No calculator + 21 Calculate the electric potential at a point 0.30 m from a point charge of +5.0 μC. Use k = 8.99 × 10⁹ N m² C⁻². Easy 3 marks Calculator + 22 Marking analysis: A learner attempts the following task: “Calculate the electric potential at a point 0.30 m from a point charge of +5.0 μC. Use k = 8.99 × 10⁹ N m² C⁻².” Their response addresses only this point: “Uses V = kQ/r.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks. Marking analysis Easy 3 marks Calculator + 23 Define capacitance, and calculate the capacitance of a capacitor that stores a charge of 6.0 × 10⁻⁴ C when the potential difference across it is 12 V. Easy 3 marks Calculator + 24 Marking analysis: A learner attempts the following task: “Define capacitance, and calculate the capacitance of a capacitor that stores a charge of 6.0 × 10⁻⁴ C when the potential difference across it is 12 V.” Their response addresses only this point: “Defines capacitance as the charge stored per unit potential difference: C = Q/V.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks. Marking analysis Easy 3 marks Calculator + 25 Calculate the energy stored in a 5.0 × 10⁻⁵ F capacitor when it is charged to a potential difference of 12 V. Easy 3 marks Calculator + 26 Marking analysis: A learner attempts the following task: “Calculate the energy stored in a 5.0 × 10⁻⁵ F capacitor when it is charged to a potential difference of 12 V.” Their response addresses only this point: “Uses energy = ½CV².” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks. Marking analysis Easy 3 marks Calculator + 27 Define gravitational potential at a point, and calculate the gravitational potential at the surface of a planet of mass 6.0 × 10²⁴ kg and radius 6.4 × 10⁶ m. Use G = 6.67 × 10⁻¹¹ N m² kg⁻². Medium 4 marks Calculator + 28 Marking analysis: A learner attempts the following task: “Define gravitational potential at a point, and calculate the gravitational potential at the surface of a planet of mass 6.0 × 10²⁴ kg and radius 6.4 × 10⁶ m. Use G = 6.67 × 10⁻¹¹ N m² kg⁻².” Their response addresses only this point: “Defines gravitational potential as the work done per unit mass to bring a small test mass from infinity to that point.” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks. Marking analysis Medium 4 marks Calculator + 29 A straight wire of length 0.50 m carries a current of 4.0 A perpendicular to a uniform magnetic field of flux density 0.20 T. Calculate the magnetic force on the wire. Easy 3 marks Calculator + 30 Marking analysis: A learner attempts the following task: “A straight wire of length 0.50 m carries a current of 4.0 A perpendicular to a uniform magnetic field of flux density 0.20 T. Calculate the magnetic force on the wire.” Their response addresses only this point: “Uses F = BIL for a wire perpendicular to the field.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks. Marking analysis Easy 3 marks Calculator + Self-assessed Not marked yet
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