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MAGNETISM & ELECTROMAGNETISM

Chapter – 14

Q.1: What is flux density and how is it related to the number of lines of induction expressed in Webers?
Ans: Magnetic flux density $B$ is the magnetic flux per unit area $(B = \Phi / A)$ . The unit of flux density is Weber per $m^2$ (or tesla, $T$ ). Magnetic flux is the total number of magnetic lines of induction passing perpendicularly through an area $(\Phi = B \times A)$ . Its SI unit is ‘Weber’ $(1 Wb = 1 T \cdot m^2)$ . Hence magnetic flux density refers to the number of lines of induction (in Webers) per square meter.

Q.2: Charged particles fired in a vacuum tube hit a fluorescent screen. Will it be possible to know whether they are positive or negative?
Ans: Yes, the charge on particles in motion can be found by applying a magnetic field perpendicular to the motion of the charges and by observing the deflection. A positive charge in an inward perpendicular magnetic field is deflected upward. In an electric field, a positive charge will be deflected towards the negative side (plate).

CURRENT ELECTRICITY

Chapter – 13

Q.1: Electrons leave a dry cell and flow through a lamp back to the cell. Which terminal the positive or negative is the one from which electrons leave the cell? In which direction is the conventional current?
Ans: Electrons leave the negative terminal of the cell and move towards the positive terminal. However, as a convention, the conventional current is assumed to be the consisted of positive electric charges moving from a positive terminal to the negative terminal change flowing through the area per unit time (I = q/t).

Q.2: Both p.d. and e.m.f. are measured in volts. What is the difference between these concepts?
Ans: P.d. is the work done per unit charge across resistor in a closed circuit. But e.m.f. the total p.d. across the external and internal resistance, it refers to a source of current and is greater than the potential drop in an external circuit. (e.m.f. p.d. + internal resistance drop)

Electrostatics - Question Answers - Physics XII

Chapter – 12

Q.1: Repulsion is the sure test of electrification. Explain?
Ans: Electrostatic attraction is observed between oppositely charged bodies and also between a charged (+ve or -ve) and an uncharged body. But, however, only two charges of the same kind (both +ve or both -ve) can repel each other. Hence, repulsion is the sure test of electrification.

Q.2: Will a solid metal sphere hold a large electric charge than a hollow sphere of the same diameter? Where the charge does resides in each case?
Ans: A solid metal sphere will hold the same amount of charge as is held by a hollow sphere of the same diameter. This is due to the fact that any excess electric charge resides only on the outer surface of a conductor.

Questions Answer (Q/A)

Chapter - 11

Q.1: How do you distinguish between temperature and heat? Give example?
Ans: Heat is the energy flowing between bodies and surroundings due to the difference of temperature. But temperature is a measure of the average translation kinetic energy of the molecules of a body. If we dip a red hot iron ball in the sea, heat will flow. The amount of internal energy possessed by the ball is very small as compared to the immense amount contained in the sea.

Q.2: Why is the earth not in thermal equilibrium with the sun?
Ans: The earth is not in thermal equilibrium with the sun; because while the earth is being warmed by the absorbed radiant energy, it is also losing heat in various ways (e.g. re-radiation, conduction, convection and evaporation). Moreover, they are not in perfect thermal contact with each other. The average temperature of the earth is about 300 K.

PHYSICS 9TH - Short / Detailed Question Answers

Q.1: What is Science?

Ans: Science:
The word science refers to the study of a fact by collecting information through observation, presenting it in a mathematical way, justifying the idea with experiment, and finally making a conclusion about the fact.

Q.2: Define Physics.

Ans: Physics:
One of the most basic and ancient sciences is Physics. It can be defined as: Physics is the branch of science which observes the nature, represents it mathematically, and concludes with the experiment.

In other words, Physics is the branch of science that deals with studies of matter, its composition, properties, and interaction with energy.

DIRECT AND INDIRECT SPEECH: COMMANDS AND REQUESTS

ENGLISH 10TH - Language Practice

UNIT # 8.3

Q.
A relative pronoun is used to connect a clause or phrase to a noun or pronoun. The clause modifies or describes the noun. The most common relative pronouns are who, whom, whose, which, and that. Sometimes, ‘when’ and ‘where’ can be used as relative pronouns as well.

SAFETY MEASURES THAT CAN SAVE YOUR LIFE

ENGLISH 10TH - Short Question Answers

UNIT # 8.1

Q.1: What are the main causes of road accidents?
Ans. One of the key reasons for road accidents is over-speeding; the other is the disregard for traffic rules.

Q.2: What two important safety measures can save people’s lives?
Ans. Two important safety measures that can save people’s lives and protect them from disability are wearing helmets and fastening seat belts.

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