GCSE Physics Specification

OCR A J249

Section P7.2: Power and efficiency

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#P7.2a

describe, with examples, the process by which energy is dissipated, so that it is stored in less useful ways

#P7.2b

describe how, in different domestic devices, energy is transferred from batteries or the a.c. from the mains

how energy may be wasted in the transfer to and within motors and heating devices

#P7.2c

describe, with examples, the relationship between the power ratings for domestic electrical appliances and how this is linked to the changes in stored energy when they are in use

#P7.2d

calculate energy efficiency for any energy transfer

#P7.2e

describe ways to increase efficiency

#P7.2f

explain ways of reducing unwanted energy transfer

lubrication and thermal insulation

#P7.2g

describe how the rate of cooling of a building is affected by the thickness and thermal conductivity of its walls (qualitative only)