Resistance and Temperature - Chapter 4 Electric Current

Flashcards covering key concepts from Chapter 4 on electric current, resistance, temperature coefficients in metals and intrinsic semiconductors, thermistors, and diodes.

How does the resistance of a metal change as its temperature increases?

The resistance of a metal increases with an increase of temperature.

Why does the resistance of a metal increase when its temperature is increased?

The positive ions in the conductor vibrate more, which means the charge carriers (conduction electrons) cannot pass through the metal as easily when a $\text{pd}$ is applied across the conductor.

Why is a metal said to have a positive temperature coefficient?

Because its resistance increases with an increase of temperature.

How does the resistance of an intrinsic semiconductor change as its temperature increases?

The resistance of an intrinsic semiconductor decreases with an increase of temperature.

Why does the resistance of an intrinsic semiconductor decrease when the temperature is increased?

Because the number of charge carriers (conduction electrons) increases when the temperature is increased.

Why does a thermistor made from an intrinsic semiconductor have a negative temperature coefficient?

Because its resistance decreases with an increase of temperature.

How does the percentage change of resistance per kelvin change of temperature for a thermistor compare to that for a metal?

Its percentage change of resistance per kelvin change of temperature is much greater than for a metal.

What is a thermistor often used for due to its resistance properties?

Thermistors are often used as the temperature-sensitive component in a temperature sensor.

What does a diode need in order to conduct?

A diode needs a certain $\text{pd}$ to conduct.