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1

Resistance increases with ____

Resistance increases with temperature

2

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

3

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

4

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

5

Potential difference = ?

Potential difference = current x resistance

6

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' .

7

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

8

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

That the resistance is changing

9

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

10

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