O-LevelPhysicsElectricity5054/21 · May/June 2015 · Q86 Marks
Fig. 8.1 shows the basic structure of a cathode-ray oscilloscope (c.r.o.). Some parts are missing. Electrons are emitted from the filament by thermionic emission. [Figure 8.1]
- (a)Explain what is meant by thermionic emission.[2]
- (b)Electrons hit the screen at high speed. Explain how the electrons are made to travel at high speed.[2]
- (c)The spot on the screen is made to move up and down and also across the screen. The parts of the c.r.o. that make this happen are not shown in Fig. 8.1. On Fig. 8.1, draw and label the parts that are needed.[2]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (May/June 2015). The mark or mark type is shown in brackets.
- [1] emission of electrons
- [1] emission caused by heat/high temperature
- [1] anode positive
- [1] anode attracts/accelerates electrons or electric field between filament and anode
- [1] two sets of plates shown at 90° to each other with connection(s)
- [1] labelled y plates and x plates/time base
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