Grade 11 (Physics) Electrostatics Question Answers

 IMPORTANT QUESTION ANSWERS

Q.1. Sharp points are avoided from the electrostatic machines. Why?

 

= The surface charge density 𝜎of the body is inversely proportional to the square of the radius of curvature of the surface of the material. i.e. 𝜎∝ 1𝑟² the sharp points have very small radius of curvature (i.e. 𝑟→0) so the surface charge density at these points, can be infinitely large. So to preserve the charge for very long time, sharp points are avoided from electrostatic machine.

 

Q.2. ‘Repulsion is the sure test of charge’.  Explain.

= A charge object can attracts oppositely charged object or neutral object. So attractive property cannot confirm whether the object is neutral or oppositely charged. But repulsion between two objects takes place only when they possess similar nature of charges. Thus, the repulsion between the charges ensures that the object must contains similar charges.

 

Q.3. The tires of aircrafts are made slightly conducting. Why?

 

=The tires if aircrafts are highly charged due to friction while landing on the runway. This accumulated charge may produce spark when it gets the chance of discharging. Which can produce the fire. If the tires are slightly conducting, charge will not accumulate non them and will leak to the ground.

 

Q.4. Vehicles carrying highly inflammable material usually have metallic chains touching to the ground. Why?

=In the motion of vehicles, charges are produced due to the friction of the body with air. If large amount of charge is accumulated on the in the metallic part of the body, they may discharge due to induction with other parts and spark may produce. This spark may catch the inflammable material and get fire. To prevent this miss happening, metallic chains are hung from the vehicles to touch the ground so that any charge accumulated on the vehicle leaks to the ground.

 

Q.5. We cannot charge a conductor holding on our hand why?

 

=The charge can flow easily from one point to another in a conductor. If we try to charge a conductor holding on our hand, the produced charge on the conductor easily leaks out through our body (a good conductor of electricity) to the ground.

Hence, we cannot charge a conductor holding on our hand.

 

Q.6. Electrostatic experiments do not work well on humid days. Why?

 

=Humid air consists of large no of tiny water droplets making the air conducting medium for electricity. If charge object is exposed to such wet atmosphere, charge leaks out from the object.

 

Q.7. A body is charged positively. Does its mass increase, decrease or remains same?

 

ØA body is positively charged when it loses electrons.

ØThe mass of an electron is 9.1×10⁻³¹𝐾𝑔which is very small.

ØSo, the loss of electron is loss of certain mass therefore the mass the body is reduced.

ØHowever, the mass of electron is negligibly small in comparison with the body. So loss of mass is almost impossible to detect.

 

Q. 8. What are the basic properties of electric charge?

 

=The basic properties of charge are

Øcharge is additive

ØCharge is conserved

ØCharge is Quantized

ØLike charges repel and unlike charges attract each other.