NEET Physics Question - Electrostatics

Assertion (A): A metal sphere of radius \(1\text{ cm}\) cannot hold a charge of \(1\text{ coulomb}\) in air.

Reason (R): The dielectric strength of air (minimum field required for ionisation of a medium) is \(3\text{ MV/m}\).

Both (A) & (R) are true and the (R) is the correct explanation of the (A)

Both (A) & (R) are true but the (R) is not the correct explanation of the (A)

(A) is true but (R) is false

Both (A) and (R) are false

Solution:

Assertion (A) is true: \(1\text{ C}\) is a huge charge for a \(1\text{ cm}\) sphere.

Reason (R) is true: Air's dielectric strength is \(3 \times 10^6\text{ V/m}\). The electric field at the surface \(E = \frac{Q}{4\pi \epsilon_0 R^2}\text{ }\approx 9 \times 10^{13}\text{ V/m}\).

This field greatly exceeds air's dielectric strength, causing electrical breakdown. Thus, (R) explains (A).

Rankers Physics

Charge Capacity of a Sphere

Solution:

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