I-V Characteristics

Question 1

Fixed resistor

Answer 1

• They are designed so that their resistance is always constant, despite environment
• V is directionally proportional to current
• All wire in the circuits are considered fixed resistors, low resistance

Question 2

Filament lamp

Answer 2

• Non ohmic
• For small values of current, it acts ohmic but when the current increases, the heating effect on the metal ions cause the resistance of the component to increases

Question 3

Diodes

Answer 3

• Non ohmic
• Made from semi conductors which allow current to flow only in one direction
• When the diode is in reverse bias, it doesn’t conduct at all, and resistance across it is infinite
• Diode doesn’t conduct until a threshold value of potential difference is reached
• Resistance decreases rapidly as when potential difference is increased above threshold value due to the number of density of charge carriers increases

Question 4

Negative temperature coefficient (NCT)

Answer 4

• Some semi conductors have a NCT
• As the temperature of the material increases, the resistance of the material decreases
• Change in resistance is dramatic, so they are useful in temperature sensing circuits

Question 5

Thermistor

Answer 5

• Non ohmic
• Used to electrically measure the temperature
• Made of NCT semi conductor material
• As when current, therefore temperature increases, the resistance decreases

Question 6

Light dependant resistors (LDR)

Answer 6

• Non ohmic
• When light intensity incident on the resistor increased, the resistance of the LDR decreases