F.2 Science (Abot current)

2009-12-27 7:39 pm

Diagram: http://i1020.photobucket.com/albums/af330/wingsze29/untitled.jpg

Refer to the diagram.

1. How bright is B?
A. as bright as A + C
B. as bright as A or C
C. dimmer than A or C
D. brighter than A or C
E. none of above (why?)

2. If bulb C is disconnected, how bright is A?
A. as bright as B
B. brighter than B
C. dimmer than B
D. A goes out

Diagram: http://i1020.photobucket.com/albums/af330/wingsze29/2.jpg

Refer to the diagram.

3. What happens to the ammeter reading when the switch is closed?
A. increase
B. decrease, but will not become zero
C. remain unchanged
D. become zero

更新1:

4. Which of the following electrical devices should be connected in parallel? (1) voltmeter (2) ammeter (3) resister A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only (Why??)

更新2:

5. Which of the following application(s) of rheostats is/are correct? (1) volume controls (2) dimmers (3) joystick A. (1) only B. (2) only C. (1) and (2) only D. all of them

更新3:

Diagram: http://i1020.photobucket.com/albums/af330/wingsze29/untitled-1.jpg 6. Which bulb is brighter? (Why?)

更新4:

其實我一直都有個疑問: 就最後的diagram( http://i1020.photobucket.com/albums/af330/wingsze29/untitled-1.jpg )為例,同一個circuit上有兩個bulb,electrons負責運啲energy,咁啲electrons點知有兩個bulb,然後再將啲voltage平分?? thx a lot!

更新5:

7. Fill in the blank. In a circuit, the same current flows through components connected in ____________ .

更新6:

To 第一位回答我既好人: 我想問關於Q.1. B brighter than A or C, 咁 B's brightness 會否等於 A+C 的光度?? thx!

更新7:

All the bulb is identical. sor..

回答 (3)

[匿名]

2009-12-28 3:30 am

✔ 最佳答案

But I want to ask,is all the bulb identical?

2009-12-27 19:30:37 補充：
But I want to ask,is all the bulb identical?

2009-12-27 21:05:39 補充：
1)A(it is because the resitance of A or C is high than the resistance of A+C,so B brighter than A or C)
2)A(if the bulbs are identical,they have same voltage)
3)A(the resistance will decrease when its parallel,1/R=1/R1+1/R2+1/R3....

2009-12-27 21:05:53 補充：
4)Ammeter(the internal resistance is very low in ammeter for series wiring,if its connect in parallel,it will short circuit)

2009-12-27 21:05:59 補充：
5)C(joystick is electronic controlled devices)
6)Same(you have to know that the current of a series circuit is the same if its reststance is the same,so the brightness is the same)
7)series

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[匿名]

2009-12-31 7:16 pm

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天同

2009-12-27 10:13 pm

1. Opton D.
Bulb B shares a higher voltage than bulbs A or C (assume all bulbs are identical)

2. Option A.
Both bulbs share the same voltage.

3. Option A.
Closing of the switch lowers the resistance of the parallel arrangement of bulbs A and C. Thus increasing the current.
4. Option A.
Voltmeter is used to measure the potential difference across TWO points. Hence, it must be of high resistance (in order not to draw any current) and be connected in parallel across the two points.

5. Option C
6. Assume the two bulbs are identical, they should share the same voltage from the battery, hence are of the same brightness.

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