I-V Characteristics

What is the ideal resistance of a voltmeter

Infinite resistance

What is the ideal resistance of a ammeter

Zero resistance

What does the I-V graph for an ohmic conductor look like

What does the I-V graph for a filament lamp look like

Explain the I-V graph for a filament lamp

It’s made of a thin coil of metal wire which is designed to heat up and glow.

An increase in current increases the temperature and the resistance, which causes the current to decrease again.

What does the I-V graph for a thermistor look like

Explain the I-V graph for a thermistor

As current flows through the thermistor the thermistor heats up causing more charge carriers to be released.

Therefore the resistance of the thermistor decreases.

What is the I-V graph for a diode

Explain the I-V graph for a diode

They are designed to let current flow through one direction only.

What is forward bias

The direction in which the current can flow in a diode

What is the threshold voltage

The minimum voltage required before a diode will conduct. Energy has been used to make the charge carriers available.

What happens to the resistance in a negative coefficient resistor when the temperature increases

Decreases

What happens to the resistance in a light dependent resistor when the light intensity increases

Decreases

Why does increasing the light intensity or temperature decrease the resistance in LDR’s and Thermistors

They stimulate more charge carriers to become available