# A plate carries a charge of -5.2 μC

## Homework Statement

A plate carries a charge of -5.2 μC, while a rod carries a charge of +1.8 μC. How many electrons must be transferred from the plate to the rod so that both objects have the same charge?

N/A

## The Attempt at a Solution

So im imagining a plate and a rod touching, net charge at the touching point is 0 because of the transfer of electrons. So after a transfer of 1.8 from the rod to the plate there will be no more positive in the rod.. now there are still negatives in the plate and now the rod is completely negative. Wont the negatives then repel each other to the corner? how does neutralization happen here?

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RPinPA
Homework Helper
You're overthinking it. Don't worry about how the transfer happens. What number is halfway in between -5.2 and +1.8 (just average them)? How much do you have to change each number by to get to that middle value? That number is in $\mu C$. How many electrons corresponds to that many $\mu C$?

But in answer to your direct question, after a transfer of $1.8 \mu C$ so that the plate has $-3.4 \mu C$ and the rod has $0 \mu C$, the charge is still imbalanced, and half of the charge that's on the plate is going to transfer to the rod so that they have the same charge (under the assumptions of this problem that the charges equalize).

If you have a conductor with a net charge touching another one with no net charge, charge will transfer. There will be electric forces pushing the charge onto the neutral object, attempting to equalize the potential.

You're overthinking it. Don't worry about how the transfer happens. What number is halfway in between -5.2 and +1.8 (just average them)? How much do you have to change each number by to get to that middle value? That number is in $\mu C$. How many electrons corresponds to that many $\mu C$?

But in answer to your direct question, after a transfer of $1.8 \mu C$ so that the
hey I was reading your second part and you cut off, can you explain??

You're overthinking it. Don't worry about how the transfer happens. What number is halfway in between -5.2 and +1.8 (just average them)? How much do you have to change each number by to get to that middle value? That number is in $\mu C$. How many electrons corresponds to that many $\mu C$?

But in answer to your direct question, after a transfer of $1.8 \mu C$ so that the plate has $-3.4 \mu C$ and the rod has $0 \mu C$, the charge is still imbalanced, and half of the charge that's on the plate is going to transfer to the rod so that they have the same charge (under the assumptions of this problem that the charges equalize).

If you have a conductor with a net charge touching another one with no net charge, charge will transfer. There will be electric forces pushing the charge onto the neutral object, attempting to equalize the potential.
ok awsome explanation thank you

im getting -3.5,

(-5.2+1.8)/2 = -1.7

1.8+x = -1.7
x = -3.5

I don't get this problem

SammyS
Staff Emeritus
Homework Helper
Gold Member
im getting -3.5,

(-5.2+1.8)/2 = -1.7

1.8+x = -1.7
x = -3.5
What are the units for this answer?

What does the the problem ask for?

## Homework Statement

A plate carries a charge of -5.2 μC, while a rod carries a charge of +1.8 μC. How many electrons must be transferred from the plate to the rod so that both objects have the same charge?