Quick calculation question (1 Viewer)

[bcd]

Hey, can somebody please help me with this question:

Two long parallel conductors carry equal currents in opposite directions. The force between them is 3F.
The current in one of the conductors is doubled, but the current in the other is reduced to a third of its original value.
The distance between the conductors is halved.
What is the new force between the conductors closest to?
(A) 2F
(B) 4F
(C) 8F
(D) 16F

Okay this is what I did:
Because (F/l) = (kI1I2)/d
I multiplied 3F from the question with 2, then divided by 3 and then doubled it.

I get 4F.
But the answer is 8F.
Where did I go wrong?

 

[currysauce]

Hey, can somebody please help me with this question:

Two long parallel conductors carry equal currents in opposite directions. The force between them is 3F.
The current in one of the conductors is doubled, but the current in the other is reduced to a third of its original value.
The distance between the conductors is halved.
What is the new force between the conductors closest to?
(A) 2F
(B) 4F
(C) 8F
(D) 16F

Okay this is what I did:
Because (F/l) = (kI1I2)/d
I multiplied 3F from the question with 2, then divided by 3 and then doubled it.

I get 4F.
But the answer is 8F.
Where did I go wrong?

f= 2 x 1/3 = 2/3 8/3 = 3 = 8f


pays to look at the formula sheet eh LOL

 

[zeek]

Answer

Sorry it's a PDF, but it will help you read it better

 

[bcd]

Ugh...yeah I forgot about that thing called formula sheet.
Thanks a lot guys!
BCD