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Circuits

Circuits. The power supply provides the voltage – the energy to drive the current The circuit has resistance. Charge flows round the circuit The ‘speed’ of the charge is called the current. Current Voltage Resistance. More voltage More current More resistance Less current.

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Circuits

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  1. Circuits • The power supply provides the voltage – the energy to drive the current • The circuit has resistance. • Charge flows round the circuit • The ‘speed’ of the charge is called the current.

  2. Current Voltage Resistance • More voltage More current • More resistance Less current

  3. Quantities Symbols Units

  4. Measuring V, I , R Measures voltage V Connected in parallel V RΩ A Measures current I connected in series 12V

  5. Electrical formulas VIR V volts I R amps ohms

  6. Graphs of V-I – resistor 1 Current I 2A 1A -12V Voltage V 12V

  7. Graphs of V-I – resistor 2 Current I 2A 1A -12V Voltage V 12V 6V At 6V R = ___ At 12 V R = ___

  8. Graphs of V-I - lamp Current I 2A 1A -12V Voltage V 12V At 6V R = ___ At 12 V R = ___

  9. Graphs of V-I - diode Current I 2A 1A -12V Voltage V 12V When V is reversed R is much bigger

  10. Resistors • If V is doubled then I is doubled • R does not change – remains constant • This only works if the resistor is not allowed to get hot.

  11. Lamps • I f V is doubled I is not doubled • The resistance gets bigger • This is because the lamp gets hotter

  12. Diode • If V is reversed very little current flows • The diode allows current to flow one way only

  13. Light dependent resistors resistance LDRs are used as light sensors Light intensity

  14. Thermistor resistance Thermistors are used as heat sensors temperature

  15. Test Thursday • Units and meanings of I P V Q E t • The 5 triangles • Circuit diagram • The three graphs

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