IMAT 2023 Q60 Electrical Charges


Answer is C
How do I approach this question

As the question says" insulating", there will be no change in their charges. Therefore the charge of R1 will stay the same as it was, which is Q1.

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We should also study as what if they are not insulating spheres.
Are there any theories that we can use?

If the question said the spheres were conducting;

( (Q1 + Q2) / (R1 + R2) ) x R1

We can find the total charge, divide it with the sum of the radii and multiply it with the destined radius.
Think of it as you are distributing some total amount of money among 2 siblings relative to their ages.

The answer would have been;

(Q1xR1 + Q2R1) / (R1 + R2)

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Thanks for that!
But I guess that is out of range of IMAT?