I-V 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

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 unit of measurement for resistance?

• Voltage

• Ampere

• Watts

• Ohms

What is Resistance?

• the degree to which a circuit component opposes the passage of an electric current, causing energy dissipation
• How hard the energy is pushed
• The amount of charges that pass by a given point per second
• None of the above

the formula to find current when the values of V and R are known is

• I = V²R

• I = V/R

• I = R/V

• I=VR