# Homework Help: Electricity & charge

1. Jul 24, 2017

### Cici2017

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
I chose B because I thought the positive charges in the insulator would attract the negative charges in the conductor to one side. I do realise that it is earthed for a short time. What difference does it make?

Thank you

2. Jul 24, 2017

### mjc123

What happens when "the insulator is removed"?

3. Jul 24, 2017

### Cici2017

The negative charges redistribute themselves evenly around the conductor?

4. Jul 24, 2017

### mjc123

Yes

5. Jul 24, 2017

### Cici2017

Oh~so 'earthing' has the same effect as removing the insulator?

6. Jul 24, 2017

### mjc123

No. Earthing allowes the (previously isolated) conductor to acquire a negative charge as a result of attraction from the positively charged insulator. Then the earth is disconnected (the question doesn't say this explicitly, but it is implied in "earthed for a short time") and then the insulator is removed, and the negative charge is redistributed.

7. Jul 24, 2017

### Cici2017

okay, so if the insulator was not removed, the answer would have been B?

8. Jul 24, 2017

### mjc123

Yes

9. Jul 24, 2017

### Cici2017

Thank you so much!