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Current electricity The basics

Current electricity The basics. Definitions, working and measurements. Atoms in copper wire have loose valence e - : sea of delocalised electrons. R. V. Simple circuit. Enlarged piece of wire. flow of charges (electrons: e - ). Electric current:. e -. Measures current strength ( I ).

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Current electricity The basics

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  1. Current electricityThe basics Definitions, working and measurements

  2. Atoms in copper wire have loose valence e-: sea of delocalised electrons R V Simple circuit Enlarged piece of wire flow of charges (electrons: e-) Electric current: e- • Measures current strength (I) If 5e- flow into R, 5 e- come out the other side (they have less energy) A • Rate of flow of charge (Q) e- Q (Q = I t) • I = Δt e- e- LOW energy HIGH energy (1A=1Cs-1) e- e- • Connected in series(just counting charges in certain time) • Low resistance (charges are to flow easily) When battery connected: e- flows in one direction (- to +) • Measures potentialdifference(pd) in volts (V) • Measures (electrical) potential (energy) difference in volts (V) • Thus energy per charge transferred between two points W (1V=1JC-1) V = Q • Connected in parallel • High resistance (take HIGH reading of energy and LOW reading of energy and subtract to give difference). No current flows through!

  3. Atoms in copper wire have loose valence e-: sea of delocalised electrons R V Simple circuit Enlarged piece of wire flow of charges (electrons: e-) Electric current: e- • Measures current strength (I) If 5e- flow into R, 5 e- come out the other side (they just have less energy) A • Rate of flow of charge (Q) e- Q (Q = I t) • I = Δt e- (1A=1Cs-1) e- LOW energy HIGH energy • Connected in series(just counting charges in certain time) e- e- • Low resistance (charges are to flow easily) When battery connected: e- flows in one direction (- to +) • Measures potentialdifference(pd) in volts (V) • Thus energy per charge transferred between two points W (1V=1J C-1) V = Q • Connected in parallel • High resistance (take HIGH reading of energy and LOW reading of energy and subtract to give difference). No current flows through!

  4. Ohm’s Law The relationship between pd and I is established There is a ……….. ………….. between potential difference and current strength at constant temperature

  5. A R V Ohm’s Law The relationship between pd and I is investigated. Set up a table to take readings

  6. Current strenght controlled by number of cells or a reostat (variable resistor) Ohm’s law

  7. A R V Ohm’s Law cnt. proportionality direct Ohm’s law: There is a ……….. …………………. between potential difference and current strength at constant temperature (ohmic relationship) If temperature not constant – non-ohmic relationship (not straight line)

  8. Non-Ohmic Conductors (or resistors) not adhering to Ohm’s law are non-ohmic conductors

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