Home » Page 43

CBSE Call center

CBSE has set up a dedicated Call Centre for handling routine enquiries and grievances pertaining to various activities and functions of the Board. Students presently studying in various CBSE affiliated schools, candidates appearing in private examination, pass out students of CBSE Board, parents, School management, new school seeking CBSE affiliation, awardees of CBSE scholarship schemes, aspirants and applicants for NEET, JEE, CTET, JNVST and general public can approach the CBSE Call Centre for obtaining information of the procedures/rules and regulations of various activities of the Board.

Use of concept of electric potential

We already know about electric field and electric potential. We also know that electrostatic field is completely characterized by vector function E(r). The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding. Now a question arises why do we need introduction of electric potential when we already have electric field for the description of electric force between charges.

What are light emitting diodes?

A LED is a forward biased P-N junction diode which emits visible light when energized.

A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting. Introduced as a practical electronic component in 1962, early LEDs emitted low-intensity red light, but modern versions are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness.

Uses of Good and bad absorbers of Thermal radiation

1) Appetite is increased in Winters

Atmospheric temperature is reduced in winters but body temperature remains the same.So more heat is lost by the body.So we tend to eat more to make up for the loss

2)The bottom of the cooking utencils is kept black and rough

Black and rough surface absorb more heat from the burner and cooks the food rapidly

Capacitor : Uses, Unit and Formula

1) The main purpose of the capacitor is to store charge . If an instantanous strong current is to be flown in a circuit,the best way would be to connect the terminals of the circuit to a charge capacitor

2 A capacitor can store electric energy when disconnected from its charging circuit, so it can be used like a temporary battery. Capacitors are commonly used in electronic devices to maintain power supply while batteries are being changed. (This prevents loss of information in volatile memory.)

Electric field due to charged conductor

We know that electric field inside a conductor is zero and any charge the conductor may carry shall be distributed on the surface of the conductor. For our discussion consider a conductor carrying charge on its surface again consider a small surface element ds over which we can consider surface charge density ? to be approximately constant.