components and their characteristics

State two ways to measure the variation of current with pd for a component

1. Use a potential divider to vary the pd from zero

2. Use a variable resistor to vary the current to a minimum

What is an advantage of using a potential divider over a variable resistor?

The pd across the component can be reduced to zero, which is not possible with a variable resistor circuit

What is an efficient way of capturing the current and pd data?

Connect an ammeter sensor and voltmeter sensor to a data logger, which will measure and record readings, and then displays the data directly on an oscilloscope or a computer

Results of this experiment on a wire

Results of this experiment for a lamp

Results of this experiment for a thermistor

Why is the graph for the lamp not a straight line?

The heating effect. Resistance increases as it becomes hotter

What two sets of measurements are taken when investigating the characteristics of a diode?

One with the diode forward biased and one with it reverse biased

What is meant by forward biased?

The diode is connected in its forward direction, allowing current to flow through it

What is meant by reverse biased?

The diode is connected in its reverse direction, allowing only a very small current to flow.

How is the current measured when a diode is reverse biased and why

Using a milliammeter, because the current is very small

What do the results look like for a diode?

How does the resistance of a metal change with increasing temperature?

Increases

Why does the resistance of a metal increase with temperature?

The positive ions vibrate more at higher temperatures, making it harder for charge carriers to pass through when a pd is applied

What is meant by a positive temperature coefficient?

The resistance of the material increases with increasing temperature

What is meant by a negative temperature coefficient?

The resistance of a material decreases with increasing temperature

What component possesses a negative temperature coefficient?

Intrinsic semiconductors

Why does the resistance of an intrinsic semiconductor decrease with an increasing temperature?

Because the number of charge carriers increases as temperature increases

Why are thermistors preferred over metals as the temperature sensitive component in a temperature sensor?

Because the percentage change of resistance per kelvin is much greater for a thermistor than for a metal, so it is more sensitive