Test: Gold Leaf Electroscope - JEE MCQ

Gain or loss of charge in terms of few electrons each carrying very small charge is unobservable at macroscopic level.

Correct Answer :- A

Explanation :

Line charge density = λ

radius, r=R

 length of wire inside the sphere is 2 R

Now,  λdl=dθ

for total charge enclosed by radius R, ∫(O to R)Q = ∫(O to R)λdl

Q_inc = λ2R

Now, ϕ = Q_inc/ε0

= λ2R/ε0

The magnitude of charge on one electron is is 1.6 x10^-19 C. Also called electron charge.

The coulomb (symbolized C) is the standard unit of electric charge in the International System of Units (SI). It is a dimensionless quantity, sharing this aspect with the mole. A quantity of 1 C is equal to approximately 6.24 x 1018, or 6.24 quintillion.
In terms of SI base units, the coulomb is the equivalent of one ampere-second. Conversely, an electric current of A represents 1 C of unit electric charge carriers flowing past a specific point in 1 s. The unit electric charge is the amount of charge contained in a single electron.
 

When the metal terminal of an electroscope is touched with a charged object (Positive or negative), the gold leaves spread apart or diverge in a 'V'. This is because some of the charge on the object is conducted through the terminal and metal rod to the leaves.
Since they receive the same sign charge they repel each other and thus diverge. If the terminal is grounded by touching it with a finger, the charge is transferred through the human body into the earth and the gold leaves close together.

Electric charge has the dimension electric current time. The SI derived unit of electric charge is the coulomb, which is defined as an ampere second.

Since both leaves are negatively charged, they repel each other. When the rod is removed, the electroscope will remain charged because of the extra electrons added to it. Conversely, if the rod is brought near the knob but doesn't touch it, the electroscope will appear the same while the rod is near.

Earthing and Grounding are actually different terms for expressing the same concept. Ground or earth in a mains electrical wiring system is a conductor that provides a low impedance path to the earth to prevent hazardous voltages from appearing on equipment. In electrical engineering, ground or earth is the reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the earth.

Charge quantization, then, means that charge cannot take any arbitrary values, but only values that are integral multiples of the fundamental charge (charge of proton/electron). For example, in a hydrogen ion, we usually denote it with a positive sign to indicate that there's one proton more than there are electrons.

The charge on the rod is shared between the rod and the sphere when they are in contact with each other. However, on grounding the charge will flow to the earth and the charge on the sphere becomes zero