Question

Blocks A and B are identical metal blocks. Initially block A is neutral, and block B has a net charge of$\mathbf{5}\mathbf{}\mathit{n}\mathit{C}$.Using insulating handles, the blocks are moved so they touch each other. After touching for a few seconds, the blocks are separated (again using insulating handles). (a) What is the final charge of block A? (b) What happened while the blocks were in contact with each other? (1) Protons moved from block B to block A. (2) Positrons moved from block B to block A. (3) Electrons moved from block A to block B. (4) Both protons and electrons moved. (5) No charged particles moved.

Short answer

(a) The final charge on block A is $2.5nC$.

(b) Statement 3 is correct, Electrons moved from block A to block B.

Step-by-step solution

Identification of the given data

The given data is listed below as,

• The initial charge on block A is neutral.
• The initial charge on block B is,$2.5nC$

 Step 2: Significance of the movement of charge

When charge redistribution occurs between the conductors, then the movement of electrons take place from the object having negative charge to the object having positive charge or no charge.

But, the movement of protons is not possible as they require a large amount of energy to get transferred from one object to another.

(a) Determination of the final charge on block A

Blocks A and B are the conductors; hence, the excessive mobile charges will be uniformly distributed across the surface of the block. However, as the block A was neutral and the block B was charged initially, then when both the blocks came in contact, the excess charge of B got equally distributed on both the blocks, and as the

blocks are identical, then both the blocks will get an equal amount of charge that is, $2.5nC$.

When both blocks were moved to a further distance, then each of the blocks keeps their share of the excess charges, which states that the final charge of block A is.$2.5nC$.

Thus, the final charge on block A is$2.5nC$ .

(b) Explanation of the movement of the atoms when the blocks were in contact with each other

Statement (1) is incorrect as million amounts of electron volts of energy is needed to move the proton from the nucleus as they cannot move by themselves.

Statement (2) is incorrect as the positron is described as an anti-electron that is not found in the ordinary matter and if it is a mobile charge, then it will interact with electrons. Hence, the charges will not be conserved if positrons are mobile charges.

Statement (4) is incorrect as the protons cannot move by themselves as it will take a massive amount of energy to move the protons.

Statement (5) is incorrect as charge redistribution occurred while both the blocks were in contact. Hence, due to the charge redistribution, a charged particle has also moved.

Statement (3) is correct because the excess amount of the positive charge on block B attracts some electrons of block A that eventually increases the net charge.

Thus, the electrons moved from block A to block B.