Science (English Medium) Class 12 - CBSE Question Bank Solutions

Which of the following property shows the property of ferromagnetic substances?

Two identical bar magnets are fixed with their centres at a distance d apart. A stationary charge Q is placed at P in between the gap of the two magnets at a distance D from the centre O as shown in the figure. The force on the charge Q is ______.

A transformer works on the principle of ______.

For an ideal step-down transformer, the quantity which is constant for both the coils is ______.

Which among the following, is not a cause for power loss in a transformer?

An air-cored solenoid with length 30 cm, area of cross-section 25 cm2 and number of turns 800, carries a current of 2.5 A. The current is suddenly switched off in a brief time of 10^-3s. Ignoring the variation in magnetic field near the ends of the solenoid, the average back emf induced across the ends of the open switch in the circuit would be ______.

If both the number of turns and core length of an inductor is doubled keeping other factors constant, then its self-inductance will be ______.

Read the following paragraph and answer the question:

Long distance power transmissions

The large-scale transmission and distribution of electrical energy over long distances is done with the use of transformers. The voltage output of the generator is stepped up. It is then transmitted over long distances to an area sub-station near the consumers. There the voltage is stepped down. It is further stepped down at distributing sub-stations and utility poles before a power supply of 240 V reaches our homes.

Which of the following statement is true?