Physics

[abcde]

AOA!
http://www.xtremepapers.net/CIE/Cambrid ... _qp_11.pdf
Can anyone make me understand mcqs 29 and 31?
In 29, why is 5 the correct answer and in 31 why is A incorrect?

 

[beacon_of_light]

Wasalam!

See the diagram, when switch 5 is closed, the circuit is completed, while in others the circuit is not complete and go through the diagrams of crossing wires and wires joined, and you'll understand.

for q31: When the live wire comes in contact with the case, though the case is earthed, electrons will flow to the earth but the fuse will melt because a large current in excess of 4A will flow through the circuit as the current always follows an easy, low resistance path. The fuse will melt !

 

[scouserlfc]

I think ican hlp

in 31 bcs the fuse blows after the amount of current exceeds the amnt of current allowed..Originally the current flows through the earth through the earth wire then due to the exceeded amnt it blows the fuse..

hey isnt this easy skrtch out that if you close switch no 5 the current flows theough the whole circuit as positive comes to negative

 

[abcde]

Thank you! I get it now, Just one last query: In 29, isn't the circuit already complete or closed with closing switch 5? How come?

 

[XPFMember]

Assalamoalaikum!!
if we close 6 then also i think the circuit is complete.... :? too complicated circuit!

 

[scouserlfc]

I think i got it!..


Look in the link the wire crossing joined symbol and the wire crossing not joined symbol now compare this with the type of the wire in the question.

You see that the wire that is going to six is not the joined one so no current flows through the switch 6 even if switched on and C is the right answer and not D.

Hope it clears misconception

this is the link:
http://www.google.com.pk/imgres?imgurl= ... 29,r:0,s:0


This question looks a little tricky this is the first question ive seen which is based on these symbols