Questions

VOIP is an acronym for Voice Over Internet Protocol, or in more common terms phone service over the Internet.

Voice over Internet Protocol is a category of hardware and software that enables people to use the Internet as the transmission medium for telephone calls by sending voice data in packets using IP rather than by traditional circuit transmissions of the PSTN.

Here in the given options, Skype is the only voice service that enables us to talk over internet.

The credit of inventing the television goes to Philo Farnsworth.

Some more NPP Acronym stands for 

NPP New Patriotic Party

NPP Nuclear Power Plant

NPP Notice of Privacy Practices

NPP Non-Physician Practitioner

NPP New Progressive Party

NPP National Patriotic Party

NPP Notice of Proposed Procurement

NPP Neighbourhood Police Post (Singapore)

NPP Non-Paged Pool (memory)

NPP Nurse Practitioner in Psychiatry.

A Slip ring is a ring in a dynamo or electric motor which is attached to and rotates with the shaft, passing an electric current to a circuit via a fixed brush pressing against it.

Slip rings are usually made of Phosphor Bronze.

Slip ring motors usually have a 'phase-wound' rotor. This type of rotor has a 3-phase, double-layer, distributed winding consisting of coils used in alternators. The rotor core is made up of steel laminations which have slots to accommodate formed 3-single phase windings.