Components

Question 1

How is variation of current measured in a circuit?

Answer 1

a potential divider to vary the pd from zero or

a variable resistor to vary the current to a minimum

Question 2

What is the advantage of using a potential divider?

Answer 2

current through the component and the pd across it can be reduced to zero

this is not possible with a variable resistor circuit

Question 3

What does the current/voltage graph look like for a lamp? Why does it look like this?

Answer 3

s shaped

runs throuhg the origin

gradient reduces because its resistance increases as it becomes hotter

Question 4

What does the current/voltage graph look like for a thermistor?

Answer 4

low temp is lower in the top right corner but higher in the bottom left

both are straight lines and run through the origin

Question 5

What is the shape of the current/voltage graph of a resistor at a constant temperature?

Answer 5

straight line thorugh the origin

at any point, the value of V/I is the same

ie the resistance does not change

the gradient is equal to 1/R

Question 6

What are the characteristics of a diode?

Answer 6

the current is very small when the diode is reversed biased (reverse direction)

conducts easily in the forward direction above a pd above 0.6V

hardly at all below 0,6V

Question 7

Why does resistance increase when temperature increases?

Answer 7

the positive ions in the conductor vibrate more

the charge carrier cannot pass trhough the metal as easiuly when a pd is applied across the conductor

a metal is said to have a p[ositive temperature coefficient because its resistance increases with the increase of temperature

Question 8

WHat happens to the resistance of an intrinsic semiconductor?

Answer 8

resistance decreases with increase of temperature

number of charge carriers increase when the temperature increases

therefore it has a negative temperature coefficeient