Dear Combined Science (Physics) students, if you missed out on the Lenses lesson, this is a short recap video on the different images formed by a convex lens. Due to time constraint, its recorded in a very fast pace, you may want to play and pause to study the animation to slow it down.
A Physics Blog created for my students in City College. This blog has been shifted to http://www.physics.readyspacecloud.com Please use the new website for your resource in future. :)
Monday, August 15, 2011
Answer for Combined Science Physics (Practical Electricity, Magnestism, Electromagnetis) Common Test
Dear Combined Science Physics students,
As per request, below is the answer to your Practical Electricity, Magnetism & Electromagnetism CA test. All the best for your Major Test tomorrow! I am proud of your hardwork! :)
Section A MCQ
1. C 10. B
2. B 11. C
3. D 12. C
4. B 13. D
5. B 14. A
6. B 15. D
7. B 16. B
8. A 17. A
9. B 18. D
Section B Short Questions
1a.
1b.
3a. When S is closed, both metal rods are magnetized with the same polarity. [1M]
3b. The iron rod becomes demagnetized [1M] while the steel rod remains magnetized.
[1M]. The steel rod induces magnetism in the iron rod therefore due to the
attractive forces between the rods, the rods move towards each other. [1M]
3c.
The rod that attracts the pins is STEEL. [1] Because steel retains its magnetism while iron loses its magnetism[1]
4a
4b. The hammer will hit gong 1 faster and louder. [1/2]. When the circuit is closed,
more current flows through the solenoid [1/2M] and it magnetized the iron faster. [1/2M]. Hence, the electromagnet attracts the soft iron towards it and caused the hammer to strike gong 1 once faster. [1/2M]
5. [Refer to notes]
aii. According to Fleming’s Left Hand Rule, [1M] the force exerted on the wire is perpendicular [1/2M] to the direction of magnetic field and direction of current. [1/2M]
aiii. By Fleming’s Left Hand Rule, [1M] the side AB will move downwards. [1M]
As per request, below is the answer to your Practical Electricity, Magnetism & Electromagnetism CA test. All the best for your Major Test tomorrow! I am proud of your hardwork! :)
Section A MCQ
1. C 10. B
2. B 11. C
3. D 12. C
4. B 13. D
5. B 14. A
6. B 15. D
7. B 16. B
8. A 17. A
9. B 18. D
Section B Short Questions
1a.
1b.
600 W = 0.6 kW [1M]
E = 0.6 x 5
= 3kWh [1M]
2a.
Diagram -1M
| 1. Set up the experiment as shown in the diagram. [1/2 M] |
| 2. Insert the steel bar into the solenoid. [1/2 M] |
| 3. Conncect the solenoid to DC (Direct Current) Supply. [1M] |
| 4. The steel will be magnetised. |
2b.
|
|
| Steel is difficult to magnetised and difficult to demagnetised. [1M] |
|
|
| Steel is not used as a core of a circuit breaker because it cannot |
| be demagnetised easily when the current changes direction of switched off. [1M] |
3a. When S is closed, both metal rods are magnetized with the same polarity. [1M]
Therefore the 2 metal rods repel each other since like poles repel. [1M]
3b. The iron rod becomes demagnetized [1M] while the steel rod remains magnetized.
[1M]. The steel rod induces magnetism in the iron rod therefore due to the
attractive forces between the rods, the rods move towards each other. [1M]
3c.
The rod that attracts the pins is STEEL. [1] Because steel retains its magnetism while iron loses its magnetism[1]
4a
| 1 ting is heard. [1M] When the circuit is closed, current flows through the solenoid [1/2M] and it becomes an electromagnet. [1/2M] Hence, the electromagnet attracts the soft iron towards it [1/2M] and caused the hammer to strike gong 1 [1/2M] |
|
|
more current flows through the solenoid [1/2M] and it magnetized the iron faster. [1/2M]. Hence, the electromagnet attracts the soft iron towards it and caused the hammer to strike gong 1 once faster. [1/2M]
5. [Refer to notes]
[1M – for drawing attraction field lines]
[1M – for drawing the rest of field lines]
[-1/2 M for wrong direction]
[-1/2 M for overlapping field lines]
6ai. Upwards [1M]
aii. According to Fleming’s Left Hand Rule, [1M] the force exerted on the wire is perpendicular [1/2M] to the direction of magnetic field and direction of current. [1/2M]
aiii. By Fleming’s Left Hand Rule, [1M] the side AB will move downwards. [1M]
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