I-V characteristics of components (required Practical)

Question 1

what are the steps to figure out the current/voltage characteristics of circuit components

Answer 1

1. First we use the voltmeter to read the potential difference across the resistor.
2. We then use the ammeter to read the current through the resistor and record these values in a table
3. Now we adjust the variable resistor and record the new readings on the voltmeter and ammeter.
4. We need to do this several times to get a range of readings.
5. Next we switch the direction of the battery.
6. This means that the direction of the potential difference has now reversed.
7. Both the voltmeter and ammeter should now have negative values.
8. We continue taking several readings of potential difference and current.
9. At the end, we plot a graph of the current against the potential difference and get a straight line passing through 0 (we only see this if the temperature of the resistor is kept the constant

Question 2

the graph shows a line going straight through 0 what does that mean

Answer 2

This tells us that the current through a resistor is directly proportional to the potential difference.

Question 3

what are the steps to figure out the current/voltage characteristcs of a lamp

Answer 3

1. We adjust the variable resistor and read both the potential difference and the current.
2. We do this for a range of values with the battery in the forward and reverse direction.
3. in this graph the line isn’t proportional to the potential difference (because when the current temperature increases the temperature of the filament lamp increases)
4. the increased temperature causes the resistance to increase.

Question 4

what are the steps to figure out the current/voltage characteristics of a diode

Answer 4

1. we adjust the variable resist a number of times and record the potential difference and current.
2. we do this with the battery in the forward and reverse direction.
3. As the potential difference increases beyond this point, the current rises sharply.
4. With a diode we get no current if the potential difference is reversed. ( because a diode has a high resistance)

Question 5

why do you need to have an extra resistor

Answer 5

so that the diode doesn’t get easily damaged by the high current and the extra resistor will keep the current relatively low and protect the diode

Question 6

why do we have to use a mili a meter

Answer 6

because the current is soo low