Resistors and voltage. CSE1010 Jeffrey A. Meunier

Transcription

1 Resistors and voltage CSE1010 Jeffrey A. Meunier

2 Consider this circuit

3 Consider this circuit 5 Volt power supply

4 Consider this circuit A resistive load

5 Consider this circuit A resistive load (the load can be anything that uses the voltage to do work)

6 Consider this circuit 5 Volt power supply +5V

7 Consider this circuit 5 Volt power supply The + side is held +5V at a constant +5V

8 Consider this circuit 5 Volt power supply +5V The side is held at a constant

9 Voltage difference The top half of this circuit is at +5V

10 Voltage difference The top half of this circuit is at +5V The bottom half of this circuit is at

11 Voltage difference The top half of this circuit is at +5V The bottom half of this circuit is at +5V There is a difference of 5V across this resistor

12 Voltage drop +5V We say that there is a voltage drop of 5V across this resistor.

13 Two resistors +5V

14 Two resistors The voltage drop across both +5V resistors is still 5V

15 Two resistors The voltage drop across both resistors is still 5V +5V 2.5V But since the resistors have equal values, the voltage drop across each will be 2.5V

16 Two resistors +5V This kind of 2.5V circuit is called a voltage divider.

17 Two resistors Let s use nonequal resistances +5V 1KΩ 4KΩ

18 Two resistors The voltage drop across each resistor will be proportional to its resistance +5V 1KΩ 4KΩ

19 Two resistors The voltage drop across each resistor will be proportional to its resistance +5V 1KΩ 4KΩ Total resistance = 5KΩ

20 Two resistors The voltage drop across each resistor will be proportional to its resistance +5V 1KΩ 4KΩ R1 is 1/5 of the total resistance.

21 Two resistors The voltage drop across each resistor will be +5V 1KΩ proportional to its resistance 4KΩ R2 is 4/5 of the total resistance.

22 Two resistors The voltage drop across each resistor will be proportional to its resistance +5V +4V 1KΩ 4KΩ Voltage drop across R1 is 1V

23 Two resistors The voltage drop across each resistor will be proportional to its resistance +5V +4V 1KΩ 4KΩ Voltage drop across R2 is 4V

24 Two resistors +5V As long as the source is 5V, the circuit can be tapped at A and B to get a 4V source. +4V 1KΩ A 4KΩ +4V B

25 Two resistors The circuit can also be tapped at C and A to get a1v source! +5V +4V C 1KΩ A 4KΩ +5V +4V B

26 Two resistors The strange thing about voltage is that it s all relative. +5V +4V C 1KΩ A 4KΩ +5V +4V B

27 Two resistors The strange thing about voltage is that it s all relative. +1V C +1V +1V 1KΩ A 4KΩ We can re-label all -4V the voltages with respect to C and A -4V B -4V

28 Two resistors It doesn t matter what voltage you consider A to be at. +1V C +1V +1V 1KΩ A 4KΩ -4V -4V B -4V

29 Two resistors It doesn t matter what voltage you consider A to be at. C is 1 volt above it +1V -4V +1V -4V C 1KΩ A 4KΩ B +1V -4V

30 Two resistors It doesn t matter what voltage you consider A to be at. C is 1 volt above it And B is 4 volts below it. +1V -4V +1V -4V C 1KΩ A 4KΩ B +1V -4V

31 Two resistors C 1KΩ Going from B to A A gives you +4 volts 4KΩ +4V B

32 Two resistors C 1KΩ Going from B to C gives you +5 volts A 4KΩ +5V B

33 Two resistors C 1KΩ +1V Going from A to C A gives you +1 volt 4KΩ B

34 Two resistors C Reversing the direction reverses the sign. Going from C to A gives you -1 volt. 1KΩ A 4KΩ -1V B

35 Two resistors C This just means that going from C to A there is a source of -1V, which is a decrease in voltage, not an increase. 1KΩ A 4KΩ B -1V

36 Five resistors

37 Five resistors With 5 equal resistors, there is a voltage drop of 1V across each resistor.

38 Five resistors +5V With 5 equal resistors, there is a voltage drop of 1V across each resistor.

39 Five resistors With 5 equal +4V resistors, there is a voltage drop of 1V across each resistor.

40 Five resistors With 5 equal resistors, there is a voltage drop of 1V +3V across each resistor.

41 Five resistors With 5 equal resistors, there is a voltage drop of 1V across each resistor. +2V

42 Five resistors With 5 equal resistors, there is a voltage drop of 1V across each resistor. +1V

43 Ten resistors With 10 equal resistors, there is a voltage drop of 0.5V across each resistor.

44 Ten resistors With 10 equal resistors, there is a voltage drop of 0.5V +2.5V across each resistor.

45 Continuous resistor? It would be nice to have a long, continuous resistor that we could tap anywhere

46 Continuous resistor? V

47 Continuous resistor? V

48 Continuous resistor? This thing exists

49 Potentiometer Picture Schematic diagram

50 Potentiometer Picture Schematic diagram Or sometimes like this

51 Potentiometer The left and right pins are the ends of the resistor, the middle pin is the tap (sometimes called the wiper pin)

52 Potentiometer The left and right pins are the ends of the resistor, the middle pin is the tap (sometimes called the wiper pin)

53 Potentiometer The left and right pins are the ends of the resistor, the middle pin is the tap (sometimes called the wiper pin)

54 Potentiometer The left and right pins are the ends of the resistor, the middle pin is the tap (sometimes called the wiper pin)

55 Potentiometer Vin The voltage at Vout varies from up to Vout Vin depending on the position of the knob.

56 Potentiometer Vin The voltage at Vout varies from up to Vout Vin depending on the position of the knob. The arrow here simply means that the connection slides up and down

57 Potentiometer Vin The voltage at Vout varies from up to Vout Vin depending on the position of the knob. The arrow here simply means that It s not the direction the connection of the electricity slides up and downflow or anything like that.

58 Potentiometer Vin Vout