Section 6 (Electricity) - Resistance and Resistivity Flashcards Preview

AQA A Level Physics > Section 6 (Electricity) - Resistance and Resistivity > Flashcards

Flashcards in Section 6 (Electricity) - Resistance and Resistivity Deck (12)
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1

Definition of Resistivity:

The measure of how much a particular material resists current flow

2

If the area of the a wire increases, what happens to the resistivity?

The resistivity decreases as it’s easier for electrons to pass along it

3

If the length of the a wire increases, what happens to the resistivity?

Resistivity increases as it’s more difficult for current to pass through

4

Difference between Resistance and Resistivity

Resistance is a property of an object
Resistivity is a property of a material

5

What are Semiconductors?

A group of materials that aren’t as good as metals at conducting electricity. i.e. higher Resistivity.

(Because they have fewer electrons available)

6

What does the Resistance in a Thermistor (NTC) depend on?
What is the relationship between these two variables?

- Temperature
- As Resistance decreases, temperature increases. Therefore current increases.

7

What is a Superconductor?

A material which no longer has resistivity.

8

How can a material lose resistivity?

When it’s cooled down to below a critical temp called the ‘Transitional Temperature’.
Hard/Expensive to reach transitional temp as it’s very low (e.g. -250 °C)
No Resistance = No Heat Wasted

9

What are the uses of Superconductors?

Can be used to make:
- Power cables
- Strong Electromagnets (e.g. Maglev trains)
- Electronic circuits that work fast as there’s no resistance to slow current down.

10

Definition of Resistance:

The measure of how much a particular object resists current flow

11

Ohm’s Law states:

Current is directly proportional to Voltage in an Ohmic Conductor, IF physical conditions (temp) remain constant.

12

When there’s 2 resistors in parallel, to find Total Resistance you can use the formula...

Total R = (R1 x R2) / (R1 + R2)