Starter quiz
- What is the function of a diode?
- to provide a constant resistance to current
- to provide a push to electrons
- to increase the flow of current
- to allow current to flow in only one direction ✓
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- What does it mean when a diode is in reverse bias?
- the diode will make the current flow backwards
- the diode is connected to a switch that has been turned off
- the p.d. across the diode is the wrong way round for current to flow ✓
- the p.d. across the diode is the right way round for current to flow
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- Which of these has a symmetrical I-V graph for both positive and negative p.d.?
- filament lamp ✓
- LED
- diode
- resistor ✓
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- Which of the following correctly describes how a fuse wire works?
- it prevents current flowing backwards
- it allows less current than expected to flow as the p.d. is increased
- it heats up and melts when too much current flows ✓
- it emits light when a current flows
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- What is the resistance of a diode if it allows 0.16 A to flow when the p.d. across it is 0.8 V?
- 0.2 Ω
- 0.96 Ω
- 1.28 Ω
- 5.0 Ω ✓
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How does this component work?- the resistance varies depending on temperature
- the resistance varies depending on light level
- the resistance varies depending on the direction of the applied p.d.
- the resistance varies depending on the way the experimenter turns a dial ✓
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Exit quiz
The characteristics of which component are shown by this I-V graph?- a diode ✓
- a filament lamp
- a fuse
- a resistor
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- The characteristics of a diode are shown by this I-V graph. What is its threshold voltage?
- 0.0 V
- 0.6 V ✓
- 0.7 V
- 1.02 V
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- Which component has a current that increases as the p.d. across it increases, but at higher p.d.s the current does not increase as much as expected?
- a diode
- a filament lamp ✓
- a resistor
- a buzzer
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- Which component has an I-V graph that shows the current is directly proportional to the p.d. across it?
- a diode
- a light emitting diode
- a filament lamp
- a resistor ✓
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- What is the most appropriate fuse rating for a device that normally uses a current of 9 A?
- 3 A
- 5 A
- 13 A ✓
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- What happens inside a metal wire with a bigger current through it?
- free electrons move more quickly ✓
- free electrons do not move more quickly
- metal ions vibrate more vigorously ✓
- metal ions do not vibrate more vigorously
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Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- In forward–bias, a diode has a very small resistance when the p.d. is larger than the threshold voltage.
- In reverse–bias, a diode has a very large resistance and very little current can flow.
- The greater the p.d. across a component, the larger the push on electric charges in the component.
- The resistance of a component is calculated from an I–V graph using pairs of readings and the equation R = V ÷ I.
- The greater the current through a component, the larger the heating effect on it.
Common misconception
Pupils often cannot apply the main I–V graphs to similar components.
Describe how the p.d. and current in components behaves to draw out similarities that can be used to describe unfamiliar components.
Keywords
Reverse–bias - When a diode is reverse–biased, it prevents current from flowing.
Forward–bias - When a diode is forward–biased, it allows current to flow.
Threshold p.d. - The threshold p.d. is the potential difference at which a diode allows current to flow.
Fuse - A fuse is a component that has a wire that melts if the current is too high.
Ion lattice - In a solid metal, the regular and repeating pattern that metal ions are arranged in is known as an ion lattice.
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