Practice MCQ Questions and answers on Physics-GK

An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. The magnetic field disappears when the current is turned off. It is made of soft iron since it has the property of losing its magnetism very quickly. The soft iron core of the electromagnet makes the magnetic field stronger.

L = inductance is proportional to the number of turns per unit length. So self inductance becomes three times. if turns in a coil is trippled, self inductance become nine times.

Fleming's right-hand rule (for generators) shows the direction of induced current when a conductor attached to a circuit moves in a magnetic field. It can be used to determine the direction of current in a generator's windings.

A current carrying conductor, such as a metal wire, will produce a magnetic field around it because of the motion of charge within the wire itself. This motion produces or sets up a magnetic field around the wire in the form of concentric circles. This electromagnetic effect is described in physics by the Biot-Savart Law, an experimentally deduced inverse-square law. The effect is also described by Ampere’s Law, which is derived from the Biot-Savart Law.

In order to make an electromagnet you need a dry cell batteries, thin coated copper wire and iron nail.

The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons or electron emitter) and a fluorescent screen used to view images. Colour tubes use three different phosphors which emit red, green, and blue light respectively. They are packed together in stripes (as in aperture grille designs) or clusters called “triads” (as in shadow mask CRTs).

Slip rings are usually made of Phosphor Bronze.

The safest hammers are those with heads that are alloy and drop-forged steel.

A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races. The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. In general, it’s main function is to convert kinetic friction into rolling friction. It achieves this by using at least two races to contain the balls and transmit the loads through the balls.

Gear finishing operation is called burnishing.