Physics · OCR H556 · Topic 4.2

Energy, power and resistance

Circuit symbols, E.m.f. and p.d., resistance, resistivity, power.

  • 5 sub-topics
  • Taught in Year 12
  • 33 practice questions
  • 5 animated lessons
Practice questions (33) Lessons Worksheets coming soon All OCR Physics topics

What the specification says

Every sub-topic OCR 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. 4.2.1Circuit symbolsY12
  2. 4.2.2E.m.f. and p.d.Y12
  3. 4.2.3ResistanceY12
  4. 4.2.4ResistivityY12
  5. 4.2.5PowerY12

Try 3 questions

Easy, medium and hard questions from this topic, each with a worked solutions and the mark for every step. All 33 questions in this topic, free, no account needed.

Energy, power and resistance

Easy

Recognising circuit symbols · Year 12 · 1 mark

  1. A rectangle with a straight line running through it from end to end. Which component has this circuit symbol?
    (1)

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  1. Learn the symbols in families: the resistor family are all rectangles, and the diode family are all a triangle and a bar.D: A fuse

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Electric circuits

Medium

Electrical power · Year 12 · 4 marks

A device is rated 60 W, 230 V.
  1. (a)
    Calculate the current in the device when it operates normally.
    (1)
  2. (b)
    Calculate its resistance.
    (2)
  3. (c)
    Calculate the energy transferred in 2 hours, in kJ.
    (1)

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Part (a)1 mark

  1. I=0.261 AI = 0.261\ \mathrm{A}

Part (b)2 marks

  1. P=V2RP = \frac{V^2}{R}
  2. R=882 ΩR = 882\ \mathrm{\Omega}

Part (c)1 mark

  1. E=432 kJE = 432\ \mathrm{kJ}

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Electric circuits

Hard

Resistivity · Year 12 · 1 mark

  1. A metal wire is replaced by one of the same material whose length is trebled and whose diameter is halved. What happens to the resistance?
    (1)

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  1. R=ρLAR = \dfrac{\rho L}{A}, and the area depends on the diameter squared.B: It is multiplied by 12

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