4.2.1 Circuit symbols |
(a) circuit symbols
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As set out in ASE publication Signs, Symbols and Systematics (The ASE Companion to 16–19 Science, 2000). |
(b) circuit diagrams using these symbols. |
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4.2.2 E.m.f. and p.d |
(a) potential difference (p.d.);
the unit volt |
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(b) electromotive force (e.m.f.) ε of a source such as a cell or a power supply |
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Epsilon ε is used as the symbol for e.m.f. to avoid confusion with E which is used for energy and electric field.
The ASE guide 'Signs symbols and systematics' details E as the correct symbol for e.m.f. and this will be credited in all examinations. |
(c) distinction between e.m.f. and p.d. in terms of energy transfer |
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(d) energy transfer;
W = VQ;
W = εQ.
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(e) energy transfer
eV = ½mv2
for electrons and other charged particles. |
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4.2.3 Resistance |
(a) resistance; R = V/I ; |
the unit ohm |
Learners will also be expected to recall this equation. |
(b) Ohm's law |
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(c) (i) I–V characteristics of resistor, filament lamp, thermistor, diode and light-emitting diode (LED) |
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| (c) (ii) techniques and procedures used to investigate the electrical characteristics for a range of ohmic and non-ohmic components. |
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Investigating components and analysing data using spreadsheet. |
(d) light-dependent resistor (LDR);
variation of resistance with light intensity. |
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4.2.4 Resistivity |
(a) (i) resistivity of a material;
the equation R = ρL/A |
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(a) (ii) techniques and procedures used to determine the resistivity of a metal. |
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(b) the variation of resistivity of metals and semiconductors with temperature |
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| (c) negative temperature coefficient (NTC) thermistor;
variation of resistance with temperature. |
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4.2.5 Power |
(a) the equations P = IV, P= I2R and P = R/V2 |
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| (b) energy transfer; W = VI t |
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(c) the kilowatt-hour (kWh) as a unit of energy;
calculating the cost of energy. |
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Learners will be expected to link this with 3.3.3(c) |
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