Resistance increases with ____

Resistance increases with **temperature**

Explain why restistance increases with temperature

1. When a **current **flows through a resistor, some of the **electrical **energy is **transferred into heat energy **and the resistor gets **hot**

2. This heat energy causes the **ions **in the conductor to **vibrate more**

3. This makes it **more difficult** for the charge-carrying electrons to get through the resistor - the **current can't flow **as easily and the **resistance increases**

Why, for most resistors, is there a limit to the amount of current that can flow?

**More current** means an **increase in temperature**, which means an **increase in resistance**, which means the **current decreases** again

Why does the graph with the filament lamp level off at high currents?

**More current** means an **increase in temperature**, which means an** increase in resistance**, which means that the **current decreases** again

Potential difference = ?

Potential difference = current x resistance

For the straight line V-I graphs, the resistance of the component is ____ and is equal to the ____ of the ____ of the line, or the '____' .

For the straight line V-I graphs, the resistance of the component is **steady **and is equal to the **inverse **of the **gradient **of the line, or the '**1/gradient**' .

For the straight line V-I graphs, the resistance of the component is steady and is equal to the inverse of the gradient of the line, or the '1/gradient' .

Or, in other words, the ____ the graph the ____ the resistance

The **steeper **the graph the **lower **the resistance

If line of a V-I graph curves, what does it mean?

That the **resistance **is **changing**

If the graph curves, how can the resistance be found?

FOR ANY POINT

it can be found by taking the **pair of values** (V, I) from the graph and putting them in the formula **R = V/I**

On a series circuit a voltmeter reads 6 V and a resistor reads 4 Ω. There is also an ammeter on the circuit.

What current does the ammeter measure?

V = I x R

We need to find I (the current) so we rearrange to get

I = V/R

So 6 / 4 = **1.5 A**