I-V Characteristics

Question 1

How to change direction of potential difference

Answer 1

Switch direction of battery

Question 2

3 different components used when investigating characteristics of IV graphs

Answer 2

Resistor
Diode
Filament lamp

Question 3

When resistance is constant what is the relationship between current and potential difference

Answer 3

Directly proportional
(As V=IR)

Question 4

Why is current not directly proportional to potential difference for a filament lamp

Answer 4

As current increases, the temperature of the filament lamp increases so resistance increases

Question 5

How to set up circuit

Answer 5

Power pack, ammeter and component (resistor/ filament lamp/ diode) connected in series
Voltmeter connected in parallel across component we are measuring current and potential difference for

Question 6

What is an ohmic conductor

Answer 6

A conductor for which current and potential difference are directly proportional

Question 7

Aim of investigation

Answer 7

To determine relationship between current and potential difference for a resistor, diode and filament lamp

Question 8

Method for finding relationship between current and potential difference for resistor

Answer 8

1)Set up circuit as shown in diagram (draw diagram: ammeter, power pack and resistor in series, voltmeter in parallel around resistor)
2) set potential difference on power pack to 12V, record current on ammeter and potential difference on voltmeter
3) repeat, decreasing potential difference by 1V each time down to -1
4) Plot graph with potential difference on x axis and current on y axis

Potential difference on power pack should be same as potential difference recorded on voltmeter as that is the thing you are purposely changing and controlling (the IV) however the value may slightly vary

Current then changes as potential difference changes as V=IR and for a resistor current is directly proportional to potential difference

No need to calculate resistance

Question 9

Method for finding relationship between current and potential difference for filament lamp

Answer 9

1) set up circuit as shown in diagram
2) set power pack to 12V and record current on ammeter and potential difference on voltmeter
3) repeat but decrease potential difference on power pack by 1V each time down to -12V
4) plot graph of results

Current is not directly proportional to potential difference
As current increases so does resistance because the lamp heats up so the temperature increases and higher temperature means more resistance

Question 10

How to find relationship between current and potential difference for diode

Answer 10

1) Set up circuit as shown in diagram
2) set power pack to 1wV, use ammeter your measure current and voltmeter to measure potential difference
3) repeat but decrease potential difference of power pack by 1V each time down to -12V
4) Plot graph

Question 11

True or false, we need a variable resistor

Answer 11

False
We only need a variable resistor if we can’t change the potential difference using the power pack and in that case each time we would use the variable resistor to adjust the potential difference

Question 12

2 ways to change potential difference

Answer 12

Use power pack
Use variable resistor (as sometimes potential difference of power pack is fixed and can’t be changed)

Question 13

True or false, variable resistors adjust resistance

Answer 13

False
They adjust the potential difference

Question 14

For resistor how do you keep temperature constant

Answer 14

Disconnect power supply between readings to prevent unnecessary heating