help with revision please... :)

[Steve Harding]

hey guys just wanted to quicky check with anyone, im taking my level unit 2 exam later today and ive been revising using the swindon massive site... on one of the test exams ive sure the answer is wrong and would just like someone to confirm this or tell me where im going wrong......... here is the question..

What is the CURRENT at A in the circuit shown here if R1 = 1ohm and R2 = 3ohms and VOLTAGE SUPPLY is 10v. (closest answer allowing for decimal point rounding-up) ?

[FONT=Geneva,Arial][SIZE=-1]6.68A[/SIZE][/FONT][FONT=Geneva,Arial][SIZE=-1]6.67A[/SIZE][/FONT][FONT=Geneva,Arial][SIZE=-1]2.52A[/SIZE][/FONT][FONT=Geneva,Arial][SIZE=-1]1.55A[/SIZE][/FONT]

now the answer i worked out is 13.31 A, am i correct or have i missed something ????????

 

[ezzzekiel]

1/r1+1/r2= or r1xr2/r1+r2 =

10v/0.75 = 13.3a

 

[Goody]

Yes, you are right.

Serial circuit -> Rtotal = R1+R2+....

Parallel circuit -> 1/Rtotal =1/R1+1/R2+....

In your case 1/1+1/3 = 4/3

... and therefore Rtotal = 3/4 or (.75 ohms)

I = 10 /.75

Hence I = 13.33 amps

Cheers!

 

[Steve Harding]

i knew i was right i found a couple of answers on there that where wrong... oh well.... thanks guys for you feed back..

 

[pushrod]

i knew i was right i found a couple of answers on there that where wrong... oh well.... thanks guys for you feed back..

yep there are a few questions on there where there is no correct answer at all to the question

 

[acat]

i knew i was right i found a couple of answers on there that where wrong... oh well.... thanks guys for you feed back..

If they got rid of the typing errors these questions would be a lot easier on the grey matter


Chris

 

[pmac10]

to make your calculations easier in future, in special case of TWO resistors in paralell Rt =R1*R2/R1+R2, you can normally do it in your head.

 

[Notsosmart]

to make your calculations easier in future, in special case of TWO resistors in paralell Rt =R1*R2/R1+R2, you can normally do it in your head.

Yep Product over sum is the easiest way

 

[Steve Harding]

to make your calculations easier in future, in special case of TWO resistors in paralell Rt =R1*R2/R1+R2, you can normally do it in your head.

you know i wish i had read this post before i took my exam today, i hadnt seen that way of working out parallel circuits and it came up as one of my questions.... oh well not that it mattered to much i still passed with a distinction...... get in!!!