Starter quiz
Which of the following components is represented by the circuit symbol shown?- a filament lamp ✓
- a light emitting diode
- a motor
- a laser
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- What happens to the current through a filament lamp as the p.d. across it is increased?
- it decreases
- it increases ✓
- it stays the same
- it continuously varies
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- 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?
- 0.125 Ω
- 0.5 Ω
- 0.75 Ω
- 2.0 Ω ✓
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- Which of the following statements about the I–V graph of a filament lamp is correct?
- current is on the x–axis
- resistance is on the x–axis
- p.d. is on the x–axis ✓
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- 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?
- it increases less quickly than when the p.d. across it is lower ✓
- it increases as the same rate as when the p.d. across it is lower
- it increases more quickly than when the p.d. across it is lower
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What is the resistance of the filament lamp at a p.d. of 3.0 V, according to the I–V graph shown?- 1.0 Ω
- 2.0 Ω
- 3.0 Ω ✓
- 4.0 Ω
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Exit quiz
- Which of the following components does the I–V graph shown represent?
- a resistor
- a diode
- a filament lamp ✓
- a thermistor
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- Which of the following is an ohmic conductor?
- a resistor ✓
- a filament lamp
- an electric heater
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- Which of the following statements about ohmic conductors and non–ohmic conductors is correct?
- an I–V graph for ohmic conductors is a curved line
- an I–V graph for non–ohmic conductors is a straight line
- an I–V graph for ohmic conductors is a straight line through the origin ✓
- the resistance of non–ohmic conductors is constant
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In the model of a metal shown, what do the blue circles represent?- electrons ✓
- positrons
- neutrons
- protons
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- In the model of a metal shown, what do the black circles represent?
- atoms
- electrons
- negatively charged ions
- positively charged ions ✓
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- What happens to the electrons and metal ions when a metal is heated?
- The electrons move as before and the metal ions vibrate more vigorously.
- The electrons move more quickly and the metal ions vibrate less vigorously.
- The electrons move more quickly and the metal ions vibrate as before.
- The electrons move more quickly and the metal ions vibrate more vigorously. ✓
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Worksheet
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Presentation
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Video
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.
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.
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
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