Hey there! Sign in to join this conversationNew here? Join for free
Turn on thread page Beta
    • Thread Starter
    Offline

    16
    Could someone pls help me out?
    In this mcq could someone explain to me how we got the ratio of the drift speeds? I know it's from the I = navq formula but how? TT
    The answer is A
    Name:  Screenshot (33).png
Views: 8
Size:  35.3 KB
    Offline

    9
    ReputationRep:
    I would rearrange so I can see more clearly what the drift speed depends on

    v = I/naq

    The n and q don't change so essentially we have v α I/a. The thing to watch is that if A has twice the diameter of B, then it has area a 4x as big.

    Does that help? Look for a row in the table which would fit the v α I/a relationship.
    • Thread Starter
    Offline

    16
    That clears things up a bit. Thank you =D I just don't understand one thing though. How would the area of A be 4 times as big as area of B? Why not twice?
    Offline

    9
    ReputationRep:
    Yikes, and having read it properly this time, if they're in series, the current must be the same in both, so that knocks out C and D and gives you a 50/50 chance of guessing
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: February 14, 2018
Poll
“Yanny” or “Laurel”

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.