Physics · Pearson Edexcel 9PH0 · Topic 7

Electric and magnetic fields

Electric fields, capacitors, magnetic fields and electromagnetic induction.

  • 22 sub-topics
  • Taught in Year 13
  • 247 practice questions
  • 22 animated lessons
Practice questions (247) Lessons Worksheets All Edexcel Physics topics

What the specification says

Every sub-topic Pearson Edexcel 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. 108Electric fieldsY13
  2. 109Electric field strength, E = F/QY13
  3. 110Coulomb's lawY13
  4. 111Field due to a point chargeY13
  5. 112Electric field and electric potentialY13
  6. 113Uniform field between parallel plates, E = V/dY13
  7. 114Potential in a radial fieldY13
  8. 115Field lines and equipotentialsY13
  9. 116Capacitance, C = Q/VY13
  10. 117Energy stored by a capacitorY13
  11. 118Charging and discharging capacitors and the time constantY13
  12. 119CP11: Analyse the p.d. across a charging and discharging capacitorY13
  13. 120Exponential discharge equationsY13
  14. 121Magnetic flux density, flux and flux linkageY13
  15. 122Force on a moving chargeY13
  16. 123Force on a current-carrying conductor, F = BIl sin θY13
  17. 124Induced e.m.f. from relative motionY13
  18. 125Induced e.m.f. from a changing currentY13
  19. 126Lenz's lawY13
  20. 127Faraday's lawY13
  21. 128Alternating current: frequency, period, peak and r.m.s.Y13
  22. 129Peak and r.m.s. valuesY13

Try 3 questions

Easy, medium and hard questions from this topic, each with a worked solutions and the mark for every step. All 247 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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Electric and magnetic fields

Not needed for Year 12Hard

Capacitor discharge · Year 13 · 5 marks

A 470 μF470\ \mu\mathrm{F} capacitor is charged to 12 V and then discharged through a 10 kΩ10\ \mathrm{k}\Omega resistor.
  1. (a)
    Calculate the time constant.
    (1)
  2. (b)
    Calculate the p.d. across the capacitor after 5.0 s.
    (2)
  3. (c)
    Calculate the time taken for the p.d. to fall to 3.0 V.
    (2)

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Part (a)1 mark

  1. Convert kΩ and μF to base units before multiplying.RCRC=10×103×470×10−6{}= 10 \times 10^{3} \times 470 \times 10^{-6}=4.7 s{}= 4.7\ \mathrm{s}

Part (b)2 marks

  1. During discharge, V=V0e−t/RCV = V_0\mathrm{e}^{-t/RC}.V=12e−5.0/4.7V = 12\mathrm{e}^{-5.0/4.7}
  2. Evaluate and round sensibly.V=4.1 VV = 4.1\ \mathrm{V}

Part (c)2 marks

  1. Divide by 12, take natural logs, and rearrange for tt.3.03.0=12e−t/4.7{}= 12\mathrm{e}^{-t/4.7}⇒t{}\Rightarrow t=4.7ln⁡4{}= 4.7\ln 4
  2. Falling to a quarter takes two half-lives' worth of time: 2×0.69RC2 \times 0.69RC.t=6.5 st = 6.5\ \mathrm{s}

Total5

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