IV graphs

Question 1

What components do I need to measure the resistance of a resistor?

Answer 1

• Ammeter
• Voltmeter
• Variable resistor

Question 2

Why is a variable resistor needed?

Answer 2

• Changes current of circuit
• Changes P.D across component
• GET A RANGE OF VALUES
  OR…. other way

Question 3

What are the 2 ways in this experiment that I can increase the voltage?

Answer 3

• By powerpack
• By variable resistor

Question 4

How do you collect negative results for P.D and current?

Answer 4

• Switch terminals of battery around.

Question 5

What does the straight line graph of a resistor tell you about its resistance?

Answer 5

• Shows resistance is constant.

Question 6

What is the relationship between P.D and Current in graph of resistor?

Answer 6

• Directly proportional relationship

Question 7

What is an “ohmic conductor?”

Answer 7

• One that obeys Ohms Law
• P.D and current are directly proportional and temp is constant.

Question 8

Q.)

Describe how to use variable resistor to vary the current in the circuit.

Answer 8

• Adjust the variable resistor to increase resistance through it.
• Increasing resistance through it decreases current of overall circuit.

Question 9

What happens to the brightness of the filament bulb when we increase P.D?

Answer 9

• Brightness increases
• More energy transferred

Question 10

What happens to the resistance of a filament lamp as brightness increases?

Answer 10

• Resistance increases as brightness does.

Question 11

What happens to the resistance of the lamp as you increase the P.D across it ?

Answer 11

• The resistance increases as you increase P.D.

Question 12

Why does an increase in temperature increase resistance?

Answer 12

• Metal ions vibrate more
• Flow of electrons is more difficult.
• The resistance increases.

Question 13

What causes the increase in temperature in a filament bulb?

Answer 13

The increase in current.

Question 14

How is the steepness of a line related to resistance on an IV graph?

Answer 14

• Steeper line: lower resistance
• Shallow line: high resistance

Question 15

Why does a shallow line have a high resistance?

Answer 15

• Low current for the same PD

Question 16

If the axis on IV graph changes to V on y and I on x… what happens to resistance?

Answer 16

Shallow line = low resistance
Steeper line = high resistance

low P.D. = low resistance
High P.D = high resistance

Question 17

What is the variable resistor changing when you experiment I + V in diodes?

Answer 17

• Current through diode
• see effect on P.D

Question 18

What are the steps to completing the IV experiment for diode?

Answer 18

1.) Set up electrical circuit as shown
2.) Adjust variable resistor (take new values for current + PD.)
3.) Repeat to collect 5 readings
4.) Switch terminals aroud to plot negative values
5.) Negative direction = Zero!!

Question 19

What type of resistance does diode have in poisitive direction?

Answer 19

• Low resistance

Question 20

What is a thresh hold voltage?

Answer 20

• This is the voltage needed for current to flow through.

Question 21

Why is a thresh hold voltage useful?

Answer 21

• Prevents current “accidently” flowing in opposite direction.

Question 22

Q.)

Use the Diode IV graph to explain why current passes through diode.

(3 points)

Answer 22

• It has reached thresh hold voltage
• Current flowing in correct direction
• Low resistance when voltage is positive.

Question 23

Give a descritpion of a filament lamp.

Answer 23

• Has a thin wire that heats up and emitts light.
• Non- ohmic conductor

Question 24

Q.)

How can you tell that an IV graph is a diodes’ in terms of resistance?

Answer 24

• High resistance in one direction
• Low resistance in other direction

Question 25

Which type of graph obeys Ohms Law and has a constant resistance, linear or non- linear?

Answer 25

- Linear graphs

Question 26

What are non- linear graphs?

Answer 26

- Ones that donnot obey Ohms Law and have varying resistances due to changes in temperature.

Question 27

Give examples of non- linear elements.

Answer 27

- Filament bulb - Diode - Thermistor - LDR

Question 28

Give examples of linear elements.

Answer 28

- Wire - Resistor

Question 29

What is meant by the term "negative potential difference?"

Answer 29

- Potential difference values are in opposite direction ie. negative...

Question 30

Why do we add an extra resistor when we investigate IV graphs for diodes?

Answer 30

- Lowers the current - BECAUSE the current is low we need a miliammeter.