OCR Physics electrons, waves and photons

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Yo, here are revision notes for the entire OCR Physics Electrons, Waves and Photons unit, i made it using the 2014 Physics specifications so should be quite useful. For the table of circuit symbols as you will see when you read through, you will need to draw in the symbols if you print it off.  Thanks Module 1 Electric Current  

  • Electric current is a net flow of charged particles
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  • electric current in a metal is due to the movement of electrons, whereas in an electrolyte the current is due to movement of ions.
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  • Direction of conventional current is positive to negative, the electron flow is negative to positive.
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  • Q = It
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  • Coulomb - the SI unit of charge. A charge of 1C passes a point when a current of 1 Amp flows for 1 second. 1C = 1As
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  • An ammeter put in series can measure the current in a circuit.
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  • elementary charge (e) = 1.6 x 10 ^-19
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  • Kirchoffs first law - the sum of the currents entering any point in a circuit is equal to the sum of the currents leaving that same point. Linked to the conservation of charge.
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  • Mean drift velocity - The average speed of charged particles along the length of a conductor.
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  • I = Anev
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  • Conductors have lots of charge carriers due to there outer shell making n big. semi-conductors have fewer charge carriers than metals, so the drift velocity will be higher if they have the same current, perfect insultors wouldnt have any charge carriers so n = 0
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  Module 2 Resistance       Physical quantity   Unit Prefix symbol value mass kilogram, kg pico p 10^-12 length metre, m nano n 10^-9 time second, s micro μ 10^-6 temperature kelvin, K milli m 10^-3 electric current ampere, A centi c 10^-2     kilo k 10^3     mega M 10^6     giga G 10^9     tera T 10^12         E.m.f. and p.d.

  • potencial difference - the energy lost per unit of charge by charge passing through a component. Units = JC^-1 or Volts (V)
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  • W = VQ
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  • volt = 1 Volt is 1 Joule per Coulomb
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  • A voltmeter in parallel to a component measures the p.d. across a component.
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  • electromotive force (E.m.f.) - the energy gained per unit charge by charges passing through a component. Units = JC^-1 or Volt (V)
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  • E.m.f is energy gained per unit charge and P.D. is the energe lost per unit charge.
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    Symbol   Component name Symbol Component name   Connecting lead   variable resistor   cell   microphone   battery of cells   loudspeaker   fixed resistor   fuse   power supply   earth   junction of conductors   alternating signal   crossing conductors (no connection)   capacitor   filament lamp   thermistor   voltmeter   light-dependent resistor (LDR)   ammeter   semi-conductor diode   switch   light-emitting

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