Resistance and V = I x R

Question 1

Resistance increases with ____

Answer 1

Resistance increases with temperature

Question 2

Explain why restistance increases with temperature

Answer 2

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

Question 3

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

Answer 3

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

Question 4

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

Answer 4

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

Question 5

Potential difference = ?

Answer 5

Potential difference = current x resistance

Question 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 ‘____’ .

Answer 6

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’ .

Question 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

Answer 7

The steeper the graph the lower the resistance

Question 8

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

Answer 8

That the resistance is changing

Question 9

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

Answer 9

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

Question 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?

Answer 10

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