A-LEVEL Physics: 5.1.4: Resistivity (Seneca)

Question 1

What is ‘Resistivity’?

Answer 1

The Resistivity of a Material is a Measure of how much Resistance a Material Provides.

Question 2

Different Materials offer Different ___ to the Flow of Charge.

Answer 2

Resistance.

Question 3

Resistivity is an ___ Property of a Material, Independent of its Shape or Size.

Answer 3

Intrinsic.

Question 4

Resistance = …

Answer 4

p L/A

Question 5

What are ‘Thermistors’?

Answer 5

Thermistors are Electrical Components which Change their Resistance Based on their Temperature.
Resistance is Inversely Proportional to the Temperature.
We can use Thermistors in Devices where Outputs depend on Temperature Variation.

Question 6

Types of Thermistors: (2)

Answer 6

-Positive Temperature Coefficient Thermistor. (PTC)

-Negative Temperature Coefficient Thermistor. (NTC)

Question 7

Explain ‘Negative Temperature Coefficient (NCT) Thermistors’:

Answer 7

With NTC Thermistors, the Higher the Temperature, the Lower the Resistance (inversely proportional).

Question 8

Experiment to Determine the Resistivity of a Wire: (3)

Answer 8

-1) Measure the Length of the Wire. Calculate the Cross-Sectional Area using a Micrometer (assuming the Wire’s C-SA is Circular).

-2) Set up the Wire with a Crocodile Clip that can be Reconnected to any point in the Wire.

-3) Make sure that the Current Used is Low, so the Wire doesn’t Overheat (bc this will inflate the Resistivity Result). Measure the Current & Voltage of the Wire at Multiple Lengths, & Record your Results in a Table. Calculate Resistance for each Length (V=IR).

-4) Plot your Results on a Graph. Length on x-axis, & Resistance on y-axis. Determine the Gradient of the Line to Find the Resistivity of the Wire.

Question 9

Any Amount of the Same Material Will Always have the Same…

Answer 9

Resistivity.

Question 10

Two Cylindrical Wires P and Q are of Equal Length and Made of the Same Material.
The Diameter of P is Greater than that of Q.
P and Q are Connected in Series and the Ends of this Arrangement are Connected to a Power
Supply.

Which Two Quantities are the Same for P and Q? (2)
Why?

Answer 10

-Resistivity. Because the Resistivity of a Material is the Same, regardless of size. It is an Intrinsic Property of the Material.

-Current. Because P and Q are Connected in Series. Therefore, the Current through them is the Same.