Practice MCQ Questions and answers on Physics-GK

Surge Protection Device (or surge suppressor or surge diverter) is an appliance or device designed to protect electrical devices from voltage spikes. A surge protector attempts to limit the voltage supplied to an electric device by either blocking or shorting to ground any unwanted voltages above a safe threshold.

The quartz crystal oscillates (vibrates back and forth) at a precise frequency: exactly 32768 times each second. This is due to Piezoelectric Effect. Piezoelectric Effect is the ability of certain materials to generate an electric charge in response to applied mechanical stress.

Lead exhibit superconducting phase transitions at low temperatures of 7.2 Kelvin. This discovery was made in 1913. At this temperature (known as critical temperature), the electrical resistivity of lead drops to zero. The transition is so sudden and complete that it appears to be a transition to a different phase of matter; this superconducting phase is described by the BCS theory.

A transistor transfers a signal from a low resistance to high resistance. It has two PN-junctions: one junction is forward biased and other junction is reverse biased having low resistance path and high resistance path respectively. The weak signal is introduced in the low resistance, circuit and output is taken from the high resistance circuit.

The frequency of direct current (DC) is 0 Hz, as the current only flows in one direction.

The NIOSH states "Under dry conditions, the resistance offered by the human body may be as high as 100,000 ohms.

The choke primarily serves to limit current flow to the correct level for the tube. It also can be used during startup to provide an inductive ‘kick’ forming a momentary higher-voltage pulse to start the lamp.

Both when accelerated through a potential difference of 100 kV, they will have the same energy. The mass of the electron is less than the mass of a proton, hence it will move faster(momentum).

Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor as it transitions into the superconducting state. The electrical resistivity of a metallic conductor decreases gradually as temperature is lowered. In a superconductor, the resistance drops abruptly to zero when the material is cooled below its critical temperature. An electric current flowing in a loop of superconducting wire can persist indefinitely with no power source.

A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The process is known as rectification, since it "straightens" the direction of current.