अलग-अलग धागों का उपयोग करके a, b, c, d और e अंकित पाँच गेंदें लटकाई गई हैं। युग्म (b, c) और (d, e) स्थिरवैद्युत प्रतिकर्षण दर्शाते हैं, जबकि युग्म (a, b) और (c, e) स्थिरवैद्युत आकर्षण दर्शाते हैं। यदि गेंद 'd' धनावेशित है, तो गेंद 'a' निश्चित रूप से क्या होनी चाहिए?

Which of the following statements are correct regarding electrostatic properties of conductors? A. Inside a conductor, the electrostatic field is zero. B. Electric field at the surface of a charged conductor does not depend on its surface charge density. C. The interior of a charged conductor can have no excess charge in static conditions. D. At the surface of a charged conductor, the electrostatic field must be normal to the surface at every point. E. The electrostatic potential is zero everywhere inside a charged conductor. Choose the correct answer:

What type of electric charge is acquired by a glass rod when it is rubbed with a silk cloth?