Circuit Devices

Question 1

True or false? A diode has a very high resistance in one direction

Answer 1

True

The high resistance in one direction makes it very hard for a current to flow in that direction

Question 2

What is the relationship between potential and current for a fixed resistor at a constant temperature?

Answer 2

They are directly proportional

Question 3

What happens to the resistance of a thermistor when its temperature decreases?

Answer 3

The resistance increases

Question 4

How can you use an I-V graph for a component to find the resistance of that component for a given value of current or potential difference?

Answer 4

From the graph, read off the potential difference across the component for the current given, or the current through it for the potential difference given. Then rearrange the equation V = IR to give R = V / I, and plug in your values to calculate the resistance.

Question 5

Describe and explain how the current through a filament lamp changes as the potential difference across it increases

Answer 5

As the potential difference across a filament lamp increases, the current through the lamp also increases. However, the increase in current for a given increase in potential difference becomes smaller as the potential difference (and so the current) becomes larger. This is because the increasing current increases the temperature of the filament, causing the resistance of the lamp to increase.