IV Characteristics

The graph shows the change in current with potential difference for

• an LED

• a filament lamp

• a diode

• a thermistor

To calculate the resistance of the component at a particular potential difference you

• read the current at that point on the graph and calculate p.d divided by current

• draw a tangent to the line at that point and calculate the gradient

• draw a tangent to the line at that point and calculate 1/gradient

• read the current at that point on the graph and calculate current/p.d

The resistance of the component

• is always constant as the p.d. increases

• starts high and then decreases as the p.d. increases

• starts constant for low values of p.d. and then increases as the p.d. increases

• starts constant for low values of p.d. and then decreases as the p.d. increases

Which component has the highest resistance?

• 1

• 2

The components 1 and 2 which produced this IV graph are:

• Resistors

• Filament lamps

• Diodes

• A combination of the above

To calculate the resistance of component 1

• Calculate the gradient of the line

• Calculate the gradient of line 1 and line 2 and find the difference between them.

• Calculate the area under the graph

• Calculate 1/gradient of the line

Where would you place an ammeter in the circuit?

• Green ?

• Red ?

Where would you place an ammeter in the circuit?

• Green ?

• Red ?

Where would you place a voltmeter in the circuit?

• Green ?

• Red ?

What is the relationship between the readings on Ammeters A1, A2 and A3

• A1 = A2 + A3

• A3 = A1 + A2

• A1 = A2 = A3

• A3 = A1-A2