IGCSE Physics Paper-1: Specimen Questions with Answers 107 - 109 of 149
Question number: 107
MCQ▾
Question
Three rays of light fall on a converging lens as shown.
Rays of Light Fall on a Converging Lens
Which diagram shows the path of the rays after passing through the lens?
Choices
| Choice (4) | |
|---|---|
a. |  |
b. |  |
c. |  |
d. |  |
Answer
c.Explanation
When parallel rays incident on the converging lens, they will reflected and converged at a point another side of the lens. The distance from the converging lens to intersecting point is equal to focal length of the lens. This proper arrangement is shown in choice C.
Question number: 108
MCQ▾
Question
An electromagnet is used to separate magnetic metals from no-magnetic metals. Why is steel unsuitable as the core of the electromagnet?
Choices
| Choice (4) | |
|---|---|
a. | It has a high thermal capacity |
b. | It forms a permanent magnet |
c. | It is good conductor of electricity |
d. | It has a high density |
Answer
b.Explanation
In electromagnet when we remove current the magnetic field should be removed. But if we take steel as the core of the electromagnet and starts the current the steel will magnetized and although current will off, the steel will be permanent magnet.
Question number: 109
MCQ▾
Question
How can a permanent magnet be demagnetized?
Choices
| Choice (4) | |
|---|---|
a. | cool the magnet for a long time |
b. | heat the magnet |
c. | pass a small current through the magnet |
d. | leave the magnet in a coil which carries direct current |
Answer
b.Explanation
In permanent magnet alignment of the domain properly unidirectional. To demagnetize the permanent magnet these alignment of the domain should be random. So by heating the magnet domain arranged randomly and it is demagnetized.