Physics · AQA 7408 · Topic 3.7

Fields and their consequences

Gravitational and electric fields, capacitors, magnetic fields and electromagnetic induction.

  • 18 sub-topics
  • Taught in Year 13
  • 227 practice questions
  • 18 animated lessons
Practice questions (227) Lessons Worksheets All AQA Physics topics

What the specification says

Every sub-topic AQA can examine in this topic, with its reference number from the official specification. The Y12 and Y13 tags show when each sub-topic is usually taught.

  1. 3.7.1 Fields
  2. 3.7.1FieldsY13
  3. 3.7.2 Gravitational fields
  4. 3.7.2.1Newton's lawY13
  5. 3.7.2.2Gravitational field strengthY13
  6. 3.7.2.3Gravitational potentialY13
  7. 3.7.2.4Orbits of planets and satellitesY13
  8. 3.7.3 Electric fields
  9. 3.7.3.1Coulomb's lawY13
  10. 3.7.3.2Electric field strengthY13
  11. 3.7.3.3Electric potentialY13
  12. 3.7.4 Capacitance
  13. 3.7.4.1CapacitanceY13
  14. 3.7.4.2Parallel plate capacitorY13
  15. 3.7.4.3Energy stored by a capacitorY13
  16. 3.7.4.4Capacitor charge and dischargeY13
  17. 3.7.5 Magnetic fields
  18. 3.7.5.1Magnetic flux densityY13
  19. 3.7.5.2Moving charges in a magnetic fieldY13
  20. 3.7.5.3Magnetic flux and flux linkageY13
  21. 3.7.5.4Electromagnetic inductionY13
  22. 3.7.5.5Alternating currentsY13
  23. 3.7.5.6The operation of a transformerY13

Try 3 questions

Easy, medium and hard questions from this topic, each with a worked solutions and the mark for every step. All 227 questions in this topic, free, no account needed.

Electric and magnetic fields

Not needed for Year 12Easy

Electric fields · Year 13 · 3 marks

A small positive test charge is placed near a charged sphere.
  1. (a)
    Define an electric field.
    (1)
  2. (b)
    Describe the field lines around an isolated positive point charge.
    (2)
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Part (a)1 mark

  1. A region in which a charged particle experiences a force.

Part (b)2 marks

  1. Radial, pointing outwards,
  2. closer together nearer the charge (the field is stronger).

Total3

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Electric and magnetic fields

Not needed for Year 12Medium

Coulomb's law · Year 13 · 4 marks

Two point charges of 2.0×10−62.0 \times 10^{-6} C and 4.0×10−64.0 \times 10^{-6} C are 0.3 m apart.
  1. (a)
    Calculate the force between them, and state whether it is attractive or repulsive.
    (3)
  2. (b)
    State the force if the separation is halved.
    (1)

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Part (a)3 marks

  1. FF=Q1Q24πε0r2{}= \frac{Q_1Q_2}{4\pi\varepsilon_0r^2}
  2. F=0.799 NF = 0.799\ \mathrm{N}
  3. Repulsive.

Part (b)1 mark

  1. F=3.20 NF = 3.20\ \mathrm{N}

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Gravitational fields

Not needed for Year 12Hard

Geostationary orbit · Year 13 · 4 marks

A geostationary satellite orbits the Earth once every 24 hours. Mass of the Earth =5.97×1024= 5.97 \times 10^{24} kg, radius of the Earth =6.37×106= 6.37 \times 10^{6} m, GG=6.67×10−11 N m2 kg−2{}= 6.67 \times 10^{-11}\ \mathrm{N\,m^2\,kg^{-2}}.
  1. Show that the height of the satellite above the Earth's surface is about 3.6×1073.6 \times 10^{7} m.
    (4)
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  1. Gravity provides the centripetal force that keeps the satellite in its circle.GMmr2\dfrac{GMm}{r^2}=mr(2πT)2{}= mr\left(\dfrac{2\pi}{T}\right)^2
  2. Cancel mm, rearrange for r3r^3, and convert 24 hours to seconds.r3=GMT24π2r^3 = \dfrac{GMT^2}{4\pi^2}, with T=86 400T = 86\,400 s
  3. Take the cube root. This is measured from the centre of the Earth.r=4.22×107 mr = 4.22 \times 10^{7}\ \mathrm{m}
  4. Subtract the Earth's radius to get the height above the surface.Height =4.22×107= 4.22 \times 10^{7}−6.37×106{}- 6.37 \times 10^{6}=3.59×107 m{}= 3.59 \times 10^{7}\ \mathrm{m}

Total4

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