Resistance of a hot metal
I can explain why the resistance of a metal filament changes as the p.d. across it increases.
- Year 10
- AQA
Resistance of a hot metal
I can explain why the resistance of a metal filament changes as the p.d. across it increases.
Lesson details
Key learning points
- As the p.d. across a filament lamp increases, it gets hotter and current through it increases in a non-ohmic way.
- The greater the p.d. across a filament lamp, the greater its resistance.
- A metal is made of a lattice of positively charged ions with negatively charged electrons between.
- As a current flows through metal, electrons moving through the ion lattice cause it to vibrate more vigorously.
- The more vigorously the ions (ion lattice) vibrate, the hotter the metal and the higher its resistance.
Keywords
Filament lamp - a type of lamp that uses a hot wire to emit light
Ohmic conductor - a conductor for which the current is directly proportional to the p.d.
Directly proportional - a relationship between variables in which one is a multiple of the other
Metal ion - a metal atom that has lost one or more outer electrons and has become positively charged
Free electron - an electron from the outer shell of an atom that is free to move from ion to ion through a metal
Common misconception
The gradient of an I-V graph is equal to 1/R because I = V ÷ R.
Explain how the equation for a straight line graph y = mx + c does not apply in this case because the graph is not a straight line.
Licence
Lesson video
Loading...
Prior knowledge starter quiz
6 Questions
Q1.Which of the following components is represented by the circuit symbol shown?
Q2.What happens to the current through a filament lamp as the p.d. across it is increased?
Q3.What is the resistance of a filament lamp if it has a current of 0.25 A when a p.d. of 0.5 V is applied across it?
Q4.Which of the following statements about the I–V graph of a filament lamp is correct?
Q5.If the p.d. across a filament lamp increases at a steady rate, how does the current through it change as the p.d. becomes higher?
Q6.What is the resistance of the filament lamp at a p.d. of 3.0 V, according to the I–V graph shown?
Assessment exit quiz
6 Questions
Q1.Which of the following components does the I–V graph shown represent?
Q2.Which of the following is an ohmic conductor?
Q3.Which of the following statements about ohmic conductors and non–ohmic conductors is correct?
Q4.In the model of a metal shown, what do the blue circles represent?
Q5.In the model of a metal shown, what do the black circles represent?
